I am having trouble identifying where my performance issues are coming from

Question

Here is a recording of a profiling session in Chrome. https://drive.google.com/file/d/18iXCmNzooNDZLAQVnjylwG0xkDvq6IAG/view

In the recording, A 3d model is rotating, and our WebGL rendering engine is loading the progressively data as it become visible. (Yellow boxes get replaced with the actual machine).

There are several clear pauses in the profile, but they don't point to anything that I can see.

Could anyone who may be more knowledgeable on the subject take a quick look and maybe highlight areas that I should be investigating.