I was getting the same error in MT5 on demo account and strategy tester:
Press F4 (to get to MetaEditor), go to Search – find in files:
Find what: return ((ENUM_ORDER_TYPE_FILLING)OrderGetInteger(ORDER_TYPE_FILLING));
Replace with: return (ORDER_FILLING_IOC);
Press Replace in Files
Now compile all AE that you needed to change and restart MT5.
I am not sure what does this change do I am not developer. But it fixed my issues.