The PIPs are to simulate a video feed to a submarine. Video is placed inside an industrial looking monitor graphic and I want the reception to appear a bit dodgy at points. Working with the various noise and distortion effects in AE seemed a better choice.
While I would still like to understand the offline behavior previously described, I decided to render the individual PIPs as lossless with alpha from AE then drop then into Premiere. Workflow now looks like:
1) choose the subclip in Premiere and choose ‘replace with AE comp’
2) create the composition in AE
3) render to lossless avi with alpha
4) import avi into Premiere
The PIP footage isn’t very long (< 30 seconds) so render time is minimal.
Regards,
Lee