pdftex.map: fflush() failed

I have essentially the same problem as this question – but I did not switch from miktex or change anything at all, i have been using texlive 2020 since some weeks. With older version this never happened to me, now is the second time in two weeks. Last time reinstalling texlive worked for me, but I would rather find a solution.

pdftex was working fine until the .exe crashed: while building Windows (8.1) informed me that pdftex.exe is not responding. I found no way of fixing the error and not much on google. I restarted the OS, error persists. I have tried Regenerate filename database, Regenerate formats and Regenerate fontmaps in tlmgr, but error persists. The the log file states:

c:/texlive/2020/texmf-var/fonts/map/pdftex/updmap/pdftex.map
!pdfTeX error: pdflatex.exe (file c:/texlive/2020/texmf-var/fonts/map/pdftex/up
dmap/pdftex.map): fflush() failed (Invalid argument)
 ==> Fatal error occurred, no output PDF file produced!

Regenerate formats ends with the following:

fmtutil [INFO]: disabled formats: 5
fmtutil [INFO]: successfully rebuilt formats: 54
fmtutil [INFO]: total formats: 59
fmtutil [INFO]: exiting with status 0