Broken frame insertion since #436

[dnjp]

I need to read up on the recent changes to buffer and frame handling to understand what is going on, but it appears that #436 broke frame insertion. Here's a screen recording showing the difference between 9637ebf and 6ebb3f3:

https://vimeo.com/682276362/a2114cf8ae

[rjkroege]

Oops. I think that your PR #439 would fix this? Thanks for the patch. I want to try something with #439 to make sure that it fits with what I want to do to frame.

[dnjp]

Sounds good. Let me know if anything in #439 needs to change based on what you have planned.