My program get stuck in fopen() while trying to open the LCD HAL mount point.

No, the function that causes the error must be called in order to create those kind of problems. But the problems can happen long after the bugged function was called.

The only cases where I had this type of error (merging two projects causes hangs, modifying a function or changing optimisations settings makes the application crash even if said function isn't called) were cases with one form of memory corruption or another...

Could it be a hardware problem, such as a part of memory that can't be accessed?