I would be very inclined to think that your back/hip pain is related to the PMR. Over the years I've had PMR I've never had flare up pain that showed up in the exact same location. Why does the inflammation move around like that? I don't have a clue but in my experience if I start experiencing unusual pain associated with muscles or near joints I tend to look at my prednisone dose first. Each person is different but prednisone reductions of every 3-4 weeks never worked on me. I might not have a flare up immediately but the inflammation would build up and the pain would greet me once again, usually at a new location. A couple months ago I had gotten down to 3.5 mg of prednisone but started to experience pain in my neck muscles and one shoulder. After a few weeks I finally bit the bullet and jacked the dose up to 10 mg for a five days. That cleared out the inflammation/pain and then I brought my dose back down to 4.5 mg over a couple weeks. The 3.5 dose was likely just a little too low to be effective but it took time for the inflammation to build up to the point of being miserable again. Thankfully I have a rheumy who agrees that I understand how to handle my prednisone and lets me adjust the dose as needed. It's not for everyone, but I use a very slow reduction schedule that has worked for me for the most part. However, it's a constant search for the lowest EFFECTIVE prednisone dose, not a relentless reduction to zero. Here's the link for the "Dead Slow and Nearly Stop" reduction schedule I use, from the Health Unlocked website for anyone that's interested:
https://healthunlocked.com/pmrgcauk/posts/131189593/dead-slow-and-nearly-stop-reduction-plan