Blitz3d uses 100% of CPU time whether you use Flip False or not. Only using a Delay will give back CPU time to the system.
However, Flip False is unpredictable, and unpredictable is bad. I agree that there might be something in the code causing a problem. Or a very weird local driver problem.
However, Flip False is unpredictable, and unpredictable is bad. I agree that there might be something in the code causing a problem. Or a very weird local driver problem.