SO I have an a-camera that was constantly running, and a b-cam that switched on and off. They were Jam Synched, but the end result is I have 1 A camera clip, and hundreds of B-Camera clips.
I have been able to get Premiere Pro to line them up inside a single multi-camera source sequence, but it puts each b-camera clip as a separate camera. I have figured out how to go in to modify the multi-camera source sequence as a timeline, and manually pull all the b-camera clips onto the same track. However, it is a lot of work.
FWIW it may be worth trying to do this in PluralEyes. That is my go to when the synching in Premiere isn't cutting it. However, there are other problems from using PluralEyes that I only like to use it as a last resort.