The sequence is 24fps, and I have some 120fps clips mixed. They are interpreted at 24, so they are very smooth and only last a few seconds. Upon export of the sequence, the 24 clips on the interview are fine, but the b-roll clips (which are 120) only export a single still. When previewed in Premiere, it's fine.
All drivers are current
I have exported as Quicktime, H.264 and H.265 with the same results.
I haven't tried that, but here's something very odd. If I go into speed and "reverse" them they render. I stumbled onto this accidentally because I needed to pan left instead of right in one of the clips, so I reversed it and it rendered.
I'll try your suggestion later today. Thank you for the feedback.