I get the crash consistently on my computers here. The crash is the same with regedit or SysIni called from REXX. The workplace shell is unable to function after the crash.
I tried some tools from Hobbes, but mostly they behave the same. I tried quite a few boots, but all are well developed OS/2 installations with plenty of entries in OS2.INI. These systems all are working well, so I doubt there is significant corruption of any OS2.INI file.
I aslo tried rwINI from Hobbes. This is an alternative to SysIni. That works fine. SysIni works fine when booted from CD.
Perhaps SysIni (and the Prf... functions) cannot have two full-sized INI files in memory, but a tiny OS2.INI on a bootCD is OK.
Another interesting quirk is that if I boot from C:, then I cannot open C:\OS2\OS2.INI, but I can access the same file as 'USER'. The rwINI package documents this limitation. The system uses the OS2.INI file, so that will always be open while I work.