FBX with long timeline begins to corrupt animation

Has anyone worked with FBX files where all animations (from Blender) are in the one file, but the twist is that the timeline is over 10,000 frames long (5.5min @30fps)? Looking for insights into an issue we’re having where Blendshapes and other animation features begin failing after the FBX timeline exceeds 8000 roughly. Tested as working with under 8000, glitches appearing after that.

I’m aware of the multiple-fbx-file approach but we have over 500 anims and I thought the multiple-fbx-file approach required the model in each one (if we need blendshapes) adding to file size. I may be a little lost on the topic actually so if anyone could provide insights from their own experiences, I’d be really grateful.