What' s with the random DLL ACCESS VIOLATION?
It cannot possibly be the DLLs written by Microsoft.
What's with MT5?
Nevermind, I solved the problem.
These "random DLL access violations" stop appearing when I set Allow DLL imports in Tools -> Options -> Expert Advisors.
Every time when I changed the timeframe, this access violation error would appear. Until checking that option.
After checking that option, also, each time when I load my indicator (which uses a DLL), MT5 automatically checks the option Allow DLL imports in Properties indicator's window (in Safety section).