What's the crash info for the crashes? I can sometimes tell you what the problem is from that info. This post has instructions on how to get it and what it looks like:
Open Event Viewer, expand Windows Logs on the left, click on Application, wait for it to load the events, and then find the Error event for when PSOBB crashed. It'll look something like this
Code:
Exception code: 0xc0000005
Fault offset: 0x004f840e
Faulting process id: 0x167E0
Faulting application start time: 0x1DBCB733CA5E621
Faulting application path: C:\EphineaPSO\psobb.exe
Faulting module path: C:\EphineaPSO\dinput8.dll
Post only the Exception code, Fault offset, and the final component of the Faulting module path (not the full path--just whatever is after the final backslash). In my...
However, if you crash when shooting a gun offscreen, that is almost surely as DEP crash. Check the first thing in the Technical section of the FAQ:
https://ephinea.pioneer2.net/faq/#technical