Windows.
I am experiencing the same issue... Add track using "T" select External Instrument program freeze and issues the following notice!
View attachment 4166
Shut down through task manager is the only way out.
IMHO.
Disable LoopBe. No stream deck and things work as expected. To me this is pointing to Midi and LoopBe, perhaps the OP or others can check if the "T", insert track dialogue works as expected with LoopBe disabled?
This is just a guess but to my mind it's somehow related to Midi and might also be a Midi2 issue there are a lot of new balls being put into the mix ?
I have had issues with loopBe resetting free running LFO's with other software I run, so will not surprised if others are seeing problems!
Kindest regards.