I used Unity 2019.4.xx before (URP) and all spine objects performed very nicely. But since I upgraded to Unity 2021.3.xx (sorry for wrong title, how to change it?), things perform quite poorly. In scenes that run at stable 60 FPS before now runs at 20 FPS (in mobile device). In the scene, there is a "massive" spine object (that can use some optimizations), but the question is, why/how did it perform better before? I wonder is this a known issue? Is there something that works differently in Unity 2021 that causes Spine to work slower? I'm asking because even though it has the most noticeable impact only in that particular scene, but it also affects all other scenes in my game in general, because I have spine objects everywhere.

I know I can optimize that scene quite easily by splitting the spine object into several parts and bake some of the simpler parts, I'm just curious of what might be causing the slow down. Any thoughts?