I've been having the same problem. I believe this started when the app I'd installed through Testflight with the yellow dot was removed from my dock. Testflight seemed to become confused about which build it should be opening, so it picked one from my HDD at random? I was making local exports of every version already, but just today I moved them to an iCloud folder. Moving those executables back to my HDD seems to have fixed that problem, but the app no longer has the yellow dot associated with a Testflight installed app. Hope this helps someone.