When i disable the per-player block enforcement it ceases to crash, but with it enabled a crash every time on placing a thruster
ServerExtender Log: http://puu.sh/pDzob/4f6d04b416.log
Plugin Log: http://puu.sh/pDzmS/c52a19517f.log
The above logs were with concealment activated, I redid the same steps with it deactivated and i had the same result and those logs are below.
ServerExtender Log: http://puu.sh/pDzwJ/4dce93d111.log
Plugin Log: http://puu.sh/pDzuT/a455e7e58f.log
Note: i was placing a large hydrogen thruster which is also not on the block limits, Users reported it crashing from grinding down a cargo container, placing any other kind of thruster seems to crash it.
I'll do some more tests and post those logs here.
Edit: just tested with PlayerBlockEnforcementChangeOwner disabled and no crash.