mainstage mixed up my mappings

Long term issue that I'm trying to understand better. Sometimes MainStage will change the MIDI devices that I've assigned to my virtual instruments. For example:

Create 3 different MIDI inputs for some external keyboards. Let's call them A, B, & C.

Create 3 instrument channels, load up some instruments. Let's call these 1, 2, & 3.

Assign the MIDI inputs to 3 different instruments. Route them A=1, B=2, C=3.

No problems here. Everything works as expected.

Only sometimes when I reload the MainStage concert, it will have mismatched my MIDI assignments for the entire concert. So A=3, B=2, C=1 or some other shuffle. I have no idea what causes this, but it has happened to me multiple times now. All my devices show up, only the mappings are wrong.

Has anybody else had this happen to them? What causes MainStage to re-enumerate its list of MIDI devices? Seems like that list order changes, and my mappings get mixed up. Thanks for any insight.