I can only say that through Control Panel > Appearance and Personalization > Display I coud see that I am on 125 % and this is indicated as default. That is, 125 % is the default.
For me 100% is default and recommended. But that might depend on the size and resolution of your screen.
I only wanted to ask: what do you mean by design time dpi ?
With design-time I meant in which dpi setting the IDE is designed. It's the IDE that crashes on 125% dpi because it was originally designed at 100%. Most designers design at 100% because designing at another setting could cause problems when running on 100% (and it was designed on something different).
Since the IDE (and procedurelist.lfm) was designed at 100%, when displaying at 125% it needs to resize during runtime. Perhaps there is some roundoff where it can't put the toolbar correctly at the top and it gets stuck in a loop.
You can fix this quite easily yourself.
Open up ide\lazarus.lpi project.
Press Ctrl+F12 and open procedurelist.pas
Press F12 to view the form
Resize it slightly (it doesn't really matter)
Press F12 again to view the code
Choose File > Save (or Ctrl+S) to save it
Now choose Tools > Configure Builds
Choose Clean up + Build all at the top
Choose Build at the bottom
Lazarus will now recompile itself with your changed form and the ProcedureList will work
This is because you changed the procedurelist form, it is now saved with a setting of 120DPP in designtime and resizing the form work correctly now.
Of course this is a bug which still exists in trunk (development version) so it has to be corrected in the original release by someone. (hence the bug-report I submitted)