Although you know this for some clarity I’ll say that OT “banks” of 16 patterns and “midi bank change” are definitely separate so we should refer to the issue as “midi program changes (PC)” not behaving as expected for 2 synths when switching OT banks…
I’m not sure what you know or don’t know so I’ll state the following:
OT has 2 methods of sending midi program changes, one is in the global settings and sends an incremental PC according to what pattern your on, configurable for just one channel.
The other method is using the OT midi tracks which can send any PC number on any midi channel for each of the 8 midi tracks. This info is stored in the OT “part”. Each OT bank will default to part1 of that bank, each OT bank has 4 parts you can use.
To set up custom PC changes for 2 synths that will happen on OT bank change you’ll want to disable the global incremental PC send in the OT settings and setup 2 midi tracks at least on part1 of each of the 16 banks and configure them on the appropriate channels and enter the PC number that should be sent. If you are using more than one part per bank and switching to patterns linked to parts other than part1 for each bank you’ll need to configure 2 midi tracks for PC change on those parts as well. After setting this all up and hopefully have it working correctly I’d save all the parts and the project so you know you can reload the parts and or entire project if needed and not have to configure that again…
Hope this helps, maybe you’ve done all this, I don’t know…