Hello,
I have an interesting experience:

this model was created in v2, it is complex, but still easily editable.

I opened the model in v3 and tried to extrude the highlighted edge/surface...In v3 the extrude is very slow. Takes long seconds until control points are activated, and the extrude refresh rate is 5-10 seconds. Same model works perfectly in v2.

Another question:
As you can see there are a lot of half-spheres in model (rivet heads)...The model is designed for 3D print and I don't care about exact geometry. Is there a simplified replacement (spherical polyhedron?) instead of spheres? how to create such solid?