Have a mare that was off earlier this year so got a lameness exam done and ended up getting her stifles injected. She was showing symptoms of ulcers so treated her with omeprazole. Couple months later on the pattern, she was still stiff on the backside, very upright with her head, but using her hindquarters. She would just power down and get stuck. Got chiro done couples times, massage, didn't see a huge difference. Noticed she liked to rest her back left often, so got a suggestion from an osteopath that her pelvis had an anterior tilt. With their help, i believe i was able to release it (im not an expert). Took a video of her a couple days later, any suggestions?

I would treat her for EPM.  All horses have the Protozoa.  The Protozoa has to break the blood membrane barrier. One way is when horses have ulcers. Also when the horses immune system is compromised.