GarageBand not reading Midi track properly

Hello. New to the community. Having an issue with Garageband 10.3.5 on Catalina.

I had recorded a midi track using a keyboard controller and finishing by 'writing in' corrections and additions. I used a plug in from Aria for the sound I needed. It worked very well.

I was able to play this track/region several times, and able to re write some sections without issue.

A month later opened again to do some more work. Now GarageBand (or Aria Player?) is skipping some notes (not the issue of it needing to find the sound and catching up). Chords written will not play in polyphony - they toggle between the notes like a trill.

I worked around it by making a new midi track (GB electric Piano), copied and pasted the original Midi track, changed the piano to the sound from Aria Player.

If anyone knows a better way to straighten out this out I would love to hear about it!

Thanks!