Hi - the exception happens when I quite cspect so that seems "normal"!
As above, I used "mono CSpect.exe --zxnext=cspect -r -esc -tv -brk -w4 -zxnext -nextrom -map=../project.map -mmc=../../sdcard/cspect-next-2gb.img ../demo_3d.nex"
It seems to just exit back to the command prompt without running the .nex file.