Ah right. Tbh I’ve kind of sorted this issue now. I finally managed to find an old related thread on this forum, after much debate, they found it was due to ‘Quantize to Frames’ being turned off. I have to say though – that creates a new problem in existing projects where it has not previously been turned on, as you cannot freely drag to frame without constantly turning it on and off.
However, I have since started a fresh Vegas project with QtF on from the start, and the snapping has not caused me any issues, so I will regard this issue SOLVED.