Incorrect timing of MIDI notes after loop in Cubase

I’ve been scratching my head over this issue for far too long and finally found the solution, so I wanted to share it here in case anyone else tries to find it in future.

The plugin:
Outputs MIDI note data at 16th note intervals (or multiples thereof).
The symptom:
Timing was fine until Cubase looped around, after that MIDI note timing was completely out of sync.
The solution:
Disable ASIO Guard for your plugin specifically.

I’ve no idea how my Le Goog searches never showed this Steinberg forum post, but disabling ASIO Guard made everything work perfectly again.

This was particularly nasty problem because on my machines it always worked (turns out I had ASIO Guard disabled already), but my Cubase testers kept reporting it as a problem (worked fine in every other DAW).