Judging from your description of jitter between 11-22ms I would guess you have JACK configured for 22ms latency.
There will be some latency and jitter through USB but likely to be indiscernible. What you describe sounds like the MIDI / note trigger being processed at JACK period boundaries. It should be delayed by one period and triggered at the correct relative offset within the next period. This does add some latency but reduces jitter which in general is more desirable (unless latency increases too much, i.e. large buffers).
Your symptom is exactly what I resolved in the step sequencer and what @jofemodo applied to the router so either something has regressed or you have identified another workflow that needs addressing, hence why a big report is beneficial.