switch terminal action breaks (and creates...?) terminal editors when switching between terminal editors in different groups

[meganrogge]

Open latest insiders
Create new terminal editor
Split it using editor split button on top right.
Switch from one terminal to the other (several times) using CMD+P term listing.
I hope that my message is clear enough. If not don't hesitate to tell me, and I'll do a video for you on Monday.

from #10546 (comment)

[rzhao271]

Switching from terminal A to terminal B (once) results in terminal A's group picking up a new terminal, and terminal B breaking.

[Tyriar]

Can repro:

It actually breaks the left side but only because it gets moved to the right side. I suspect this is related to the recent SIDE_GROUP change. I don't think this meets the bar to push the release back as it can only happen when changing groups via ctrl/cmd+p and the fragility of that code.

It can happen the other way too:

[meganrogge]

FWIW, the SIDE_GROUP change was reverted.