Debugging weird behaviour when single stepping and stepping over

Hello everybody.

Like in the title I noticed strange behaviour while debbuging my app, the problem is that when I'm single stepping everything is fine, but then when I step over or run to cursor line on the same code I'm getting hardfault with impreciserr bus fault, also changing optimazation level from 0 to higher seems to help but I used O0 before all the time and there were no problems.

I'm really confused about that and I would appriciate any thoughts what's goining on.