It usually is null pointer (or null pointer + offset). It is too common
Perhaps some kind of UAE AmigaOS "debug" mode would be useful, for example internal segtracker like thingy (which would be nearly completely in UAE side so that debugger can easily access the data even when AmigaOS side is too corrupted) and hooking to LoadSeg() so that debugged program gets loaded to special reserved debug memory space, no more annoying changing segment addresses between debug sessions!