Cause is user error, fixing the user is beyond the scope of this forum.
Fixing equipment/code for the users are the routine jobs for the Forum Members; besides these routine jobs, the Forum members also take the tasks of fixing the users' minds by bringing them from off-track motivations in to the right-track motivations; there are examples of many successes in these efforts. I was fixed in many situations -- getting convinced based on rational examples that CLKPR is an ordinary register and not an EEPROM type register.