I have some gun shots on full auto that seem to stutter half way through at random.
There are no pitch, volume or offset randomisations to eliminate that being the cause.
My buffer is set to high and every instance of a sound is set to unlimited polyphony.
Any insights into the possible cause for the stuttering?
Have you tried recording a session in the FMOD profiler window? Doing so may reveal a large amount of useful information, such as how many voices your event is playing. This information may make it easier to determine why the issue is occurring.