There are times when the ms Timer should be used with caution.
Wait +(ms).vi is a solid routine installed to support DAQ but does suffer at ms timer rollover. (or did)
I have not inspected the underlying code of the OpenG function
the attached vi. (or it's predicessors) also has some issues in a non-deterministic OS. Cursor movements and any other OS demands may not allow "Wait +(ms).vi" OR "CCI Delay.vi" to return promptly on time. consider them BOTH to be wait AT LEAST mSec.
I have required the exclusive use of "CCI Delay.vi" (or it's predecessors) in test apps for over 7 years.