The event going as I write this is a 2000-point cap match on Alpine Peaks.
I opted to run four light mechs and focus on capping. My first drop mech was a LCT-PB with stealth armor. If/when that mech dies, every mech following that will be unable to cap.
After the third match that this had happened on, and moving different mechs into the follow-up slots in the following matches, I'm pretty certain this is the exact bug.
I did not try following the stealth LCT-PB with another stealth mech. It may be that would have worked. By the time I'd narrowed the bug down and thought to experiment, I'm done playing.