(Translated from German with the help from a web translator) In the new paint.net version 4.2.6, the pixel density can no longer be adjusted. As soon as the setting is changed and confirmed, the old setting will be displayed again the next time you open the "Picture" menu. Kind regards
"MC Painter"
Edit:
Okay, after cleaning up some temporary files and rebooting the operating system (WIN10 home 64bit) the problem seems to be fixed. So probably no bug in paint.net and I will reboot the PC after each update at first now... 😄