When I add \listfiles to the code, this is the log-file:

This is pdfTeX, Version 3.14159265-2.6-1.40.17 (TeX Live 2016) (preloaded format=pdflatex) \write18 enabled. entering extended mode (./loesch.tex LaTeX2e <2016/03/31> patch level 3 Babel <3.9r> and hyphenation patterns for 83 language(s) loaded. (/usr/local/texlive/2016/texmf-dist/tex/latex/koma-script/scrbook.cls Document Class: scrbook 2016/06/14 v3.21 KOMA-Script document class (book) (/usr/local/texlive/2016/texmf-dist/tex/latex/koma-script/scrkbase.sty (/usr/local/texlive/2016/texmf-dist/tex/latex/koma-script/scrbase.sty (/usr/local/texlive/2016/texmf-dist/tex/latex/graphics/keyval.sty) (/usr/local/texlive/2016/texmf-dist/tex/latex/koma-script/scrlfile.sty Package scrlfile, 2016/06/14 v3.21 KOMA-Script package (loading files) Copyright (C) Markus Kohm

))) (/usr/local/texlive/2016/texmf-dist/tex/latex/koma-script/tocbasic.sty) (/usr/local/texlive/2016/texmf-dist/tex/latex/koma-script/scrsize11pt.clo) (/usr/local/texlive/2016/texmf-dist/tex/latex/koma-script/typearea.sty Package typearea, 2016/06/14 v3.21 KOMA-Script package (type area) Copyright (C) Frank Neukam, 1992-1994 Copyright (C) Markus Kohm, 1994-

)) (/usr/local/texlive/2016/texmf-dist/tex/latex/koma-script/scrlayer-scrpage.sty (/usr/local/texlive/2016/texmf-dist/tex/latex/koma-script/scrlayer.sty)) (/usr/local/texlive/2016/texmf-dist/tex/generic/babel/babel.sty (/usr/local/texlive/2016/texmf-dist/tex/generic/babel-english/english.ldf (/usr/local/texlive/2016/texmf-dist/tex/generic/babel/babel.def))) (/usr/local/texlive/2016/texmf-dist/tex/latex/reledmac/reledmac.sty (/usr/local/texlive/2016/texmf-dist/tex/latex/xkeyval/xkeyval.sty (/usr/local/texlive/2016/texmf-dist/tex/generic/xkeyval/xkeyval.tex (/usr/local/texlive/2016/texmf-dist/tex/generic/xkeyval/xkvutils.tex))) (/usr/local/texlive/2016/texmf-dist/tex/latex/xargs/xargs.sty) (/usr/local/texlive/2016/texmf-dist/tex/latex/etoolbox/etoolbox.sty) (/usr/local/texlive/2016/texmf-dist/tex/latex/bigfoot/suffix.sty) (/usr/local/texlive/2016/texmf-dist/tex/generic/xstring/xstring.sty (/usr/local/texlive/2016/texmf-dist/tex/generic/xstring/xstring.tex)) (/usr/local/texlive/2016/texmf-dist/tex/generic/oberdiek/ifluatex.sty) (/usr/local/texlive/2016/texmf-dist/tex/latex/ms/ragged2e.sty (/usr/local/texlive/2016/texmf-dist/tex/latex/ms/everysel.sty)) (/usr/local/texlive/2016/texmf-dist/tex/generic/ifxetex/ifxetex.sty)) (./loesch.aux) ABD: EverySelectfont initializing macros chapter without number Section 1 (./loesch.1) (./loesch.eledsec1) Section 2 (./loesch.2) (./loesch.eledsec2) [1{/usr/local/texlive/2016/texmf-var/fonts/map/pdftex/updma p/pdftex.map}] (./loesch.aux)

File List scrbook.cls 2016/06/14 v3.21 KOMA-Script document class (book) scrkbase.sty 2016/06/14 v3.21 KOMA-Script package (KOMA-Script-dependent bas ics and keyval usage) scrbase.sty
2016/06/14 v3.21 KOMA-Script package (KOMA-Script-independent b asics and keyval usage) keyval.sty 2014/10/28 v1.15 key=value parser (DPC) scrlfile.sty 2016/06/14 v3.21 KOMA-Script package (loading files) tocbasic.sty 2016/06/14 v3.21 KOMA-Script package (handling toc-files) scrsize11pt.clo 2016/06/14 v3.21 KOMA-Script font size class option (11pt) typearea.sty 2016/06/14 v3.21 KOMA-Script package (type area) scrlayer-scrpage.sty 2016/06/14 v3.21 KOMA-Script package (end user interfac e for scrlayer) scrlayer.sty
2016/06/14 v3.21 KOMA-Script package (defining layers and page styles) babel.sty 2016/04/23 3.9r The Babel package english.ldf 2012/08/20 v3.3p English support from the babel system reledmac.sty
2016/10/04 v2.16.1 typesetting critical editions xkeyval.sty
2014/12/03 v2.7a package option processing (HA) xkeyval.tex
2014/12/03 v2.7a key=value parser (HA) xargs.sty 2008/03/22 v1.1 extended macro definitions (mpg) etoolbox.sty 2015/08/02 v2.2a e-TeX tools for LaTeX (JAW) suffix.sty 2006/07/15 1.5a Variant command support xstring.sty 2013/10/13 v1.7c String manipulations (C Tellechea) ifluatex.sty 2016/05/16 v1.4 Provides the ifluatex switch (HO) ragged2e.sty 2009/05/21 v2.1 ragged2e Package (MS) everysel.sty 2011/10/28 v1.2 EverySelectfont Package (MS) ifxetex.sty 2010/09/12 v0.6 Provides ifxetex conditional
loesch.1 loesch.eledsec1 loesch.2 loesch.eledsec2 ***********

)</usr/local/texlive/2016/texmf-dist/fonts/type1/public/amsfonts/cm/cmr10.pfb> </usr/local/texlive/2016/texmf-dist/fonts/type1/public/amsfonts/cm/cmssbx10.pfb

Output written on loesch.pdf (1 page, 24203 bytes). SyncTeX written on loesch.synctex.gz. Transcript written on loesch.log.

I have problems with the spacing of the section command in reledmac. This

\documentclass{scrbook}
\usepackage{scrlayer-scrpage}
\usepackage[english]{babel}
\usepackage{reledmac}

% Section 
\RedeclareSectionCommand[
  beforeskip=15em,
  afterskip=1em]{section}

\begin{document}

\addchap{1891}
      
        \section{Diary, 27. 4. 1891}\beginnumbering\pstart
           Met him in a bar\pend
           \endnumbering
        \section{Diary, 28. 4. 1891}\beginnumbering\pstart
          Was rather happy.\pend
           \pstart
           But not for long.\pend
           \endnumbering                            
                         
\end{document}

does not produce the desired output before and after the section command, and the \section isn't even inside the reledmac part.

output without usepackage reledmac:

output with reledmac. notice the missing space before the second section command

I have problems with the spacing of the section command in reledmac. This

\documentclass{scrbook}
\usepackage{scrlayer-scrpage}
\usepackage[english]{babel}
\usepackage{reledmac}

% Section 
\RedeclareSectionCommand[
  beforeskip=15em,
  afterskip=1em]{section}

\begin{document}

\addchap{1891}
      
        \section{Diary, 27. 4. 1891}\beginnumbering\pstart
           Met him in a bar\pend
           \endnumbering
        \section{Diary, 28. 4. 1891}\beginnumbering\pstart
          Was rather happy.\pend
           \pstart
           But not for long.\pend
           \endnumbering                            
                         
\end{document}

does not produce the desired output before and after the section command (the \section isn't even inside the reledmac part).

notice the missing space before the second section command:

I have problems with the spacing of the section command in reledmac. This works:

\documentclass{scrbook}
\usepackage{scrlayer-scrpage}
\usepackage[english]{babel}
\usepackage{reledmac}

% Section 
\RedeclareSectionCommand[
  beforeskip=15em,
  afterskip=1em]{section}

\begin{document}

\addchap{1891}
      
        \section{Diary, 27. 4. 1891}\beginnumbering\pstart
           Met him in a bar\pend
           \endnumbering
        \section{Diary, 28. 4. 1891}\beginnumbering\pstart
          Was rather happy.\pend
           \pstart
           But not for long.\pend
           \endnumbering                            
                         
\end{document}

but when i change the RedeclareSectionCommand to \baselineskip it fails:

\RedeclareSectionCommand[
  beforeskip=15\baselineskip,
  afterskip=1\baselineskip]{section}

Why is that so?

I have problems with the spacing of the section command in reledmac. This

\documentclass{scrbook}
\usepackage{scrlayer-scrpage}
\usepackage[english]{babel}
\usepackage{reledmac}

% Section 
\RedeclareSectionCommand[
  beforeskip=15em,
  afterskip=1em]{section}

\begin{document}

\addchap{1891}
      
        \section{Diary, 27. 4. 1891}\beginnumbering\pstart
           Met him in a bar\pend
           \endnumbering
        \section{Diary, 28. 4. 1891}\beginnumbering\pstart
          Was rather happy.\pend
           \pstart
           But not for long.\pend
           \endnumbering                            
                         
\end{document}

does not produce the desired output before and after the section command, and the \section isn't even inside the reledmac part.

output without usepackage reledmac:

output with reledmac. notice the missing space before the second section command