EDIT: Likely a plugin issue
This works fine in Bitwig so I think this may have something to do with renoise rather than the plug.
Create 2 identical tracks in renoise. A repeating hihat is a good example.
Add a copy of CS-3301 to each track
Without adjusting any settings press the phase button (next to blue led in picture) in one of the instances and the tracks should null to silence. So all works as expected.
Now try switching the instances between 2X oversampling on/off
In Bitwig you get a minor blip and then both tracks go back to nulling. In renoise things seem to get stuck between nulling and not and you have to keep pressing the buttons until something rights itself. My guess is that it has something to do with PDC not flagging properly to update.
When oversampling is enabled, the plugs latency jumps from 5.78ms to 14.44ms:
Track('01'): Device('VST: TBProAudio: CS3301 x64') -> 637 Samples (14.44 ms) Track('02'): Device('VST: TBProAudio: CS3301 x64') -> 255 Samples (5.78 ms)