I encountered a bug when using the A-B repeat function in the v2.0 preview (on Quest 3 headset and playback via SMB with any and all video types)
This is a little hard to explain, apologies if I made it confusing:
After setting the A start point, if you let the video play through completely without setting the B end point, when you play the video again, the previous A set point is gone, but if you try and click the A set point again it will actually create a B set point instead. Basically it half remembers the initial A set point from the first play and effectively inverts the usual AB repeat buttons.
If you then click the B set point in the options, it will create a nonsensical A set point after the B set point and cause a short loop of just a couple frames. You can still go and trick the repeat function by clearing the set points and then setting them again in backwards order (the B first and then going back earlier in the video and setting the A second).