Hi!
I just discovered you can achieve this perfectly if you use precisely 128 cycles of your wav.
An example I achieved:
A synth playing A 440hz, with a hard sync effect being automated for the duration. It’s exactly 128 cycles long.
I rendered this wav directly from my DAW and put it on the OT, set length to 1 (IE, a sinngle whole cycle) and assigned start time to the crossfader and VOILA! It works beautifully.
I tried, like you did to use length of 2 but it sounded terrible. As soon as I did 1, with 128 full cycles in the wav it works flawlessly, and beautifully.
The only problem is LFO’s don’t seem to work nicely with start time. They are super glitchy and appear to change the pitch, which is not how it should behave. It’s a darn shame… But for the moment, moving the crossfader and scanning through 128 cycles sounds amazing.
More research will be conducted! Good luck.