Success for now: I changes some "Special settings"! I did not track down now, which one gave success, but I changed the following value to 10 times the original one:
CodeExplorerLimit=2000000 HLOnUpToSize=5000000 MaxWrapSize=2000000 MultiHLOnUpToSize=3500000 -- <https://forum.pspad.com/read.php?4,67848,70339> PSPad freeware editor https://www.pspad.com
