Welcome to TE! So sorry to hear about your pain issues! Oh, I totally get it though, been there in so many areas of what you are posting...

OK, do make sure you are happy with your PT. If you don't like the first one you see, request another--better yet if a sports specific one. A great PT can teach you much. Here is my spin on your situation... I woud think part of your issue is body mechanics compensating to the old injury you mention. I have some of the same (plus a book report of other junk I'll skip for now)...

What the PT can tell you is if your body has learned to over-compensate from the old injury. Without us even realizing it, this can happen. Affects SO much.

I modify my rides all the time. If it hurts, stop... and do whatever does not!

Maybe some cross training in the pool could help tide you over under the spin issues get worked out? If you have one available. My PTs were always big on the pool. You don't even have to be a lap swimmer... just walking in the water is working it my PT told me.

I know what you mean about loving Spinning. I'm a certified Spinning instructor through MDA, besides road cycling and mtb. Pedaling is my passion lol. Well, and I'm learning to love the pool per my PT's advice .

I hope you find some resolve soon!