problem opening .fla in after effects. Frames disappearing.

Hi, I'm opening a very intense .fla project (large complex drawings and animation, but no fx) in after effects (this triggers After Effects to export every layer of the original .fla as a .swf - into a specified folder and import these into 1 composition).

I've done this for years with simpler projects and it always works fine.

However, with my current project whenever I import a .fla into after effects - it opens as a composition, I see all my layers - but random frames across the timeline on random layers are missing, just blank gaps where there should be drawings, but only on some layers. For example the background will remain but the main character will flicker in and out of existence.

When I export the .fla file as a single flat SWF it is fine, but obviously I cant edit the individual layers like this.

Has anyone experienced this?

The only solution I can think of is to export every broken layer as a PNG sequence, which isn't ideal

Specs: MBP sonoma, Animate 24.0.0 , After Effects 24.1.0