What's wrong with the Dutch Hippo?

Anyone that's been reading my blog since I still lived in PA is familiar with the Dutch Hippo. If you're not, he belongs to Riding Bestie--who you should all be familiar with as she comes up to torture play with my animals on a semi-regular basis. He's a nineteen year old Dutch Warmblood and also my spirit animal. We both enjoy going slow and eating snacks.

featured in many episodes of rob and big--rob being bobby and big being fatty memphis

Last year, towards the end of September, Memph started looking almost neurological. He was leaning left with his hind end, like it was no longer attached to his body. While just standing he would lean almost to the point of falling over, and then would quickly stand back up. At the walk he would twist his left hind inward.

I saw him about a month after he started doing this, and while it still looked like maybe something neuro, we also threw around the possibility of a pinched nerve or something similar in his hind end/spine.

what the actual fuck

The PA vet--the most useless person on the planet, but unfortunately literally the only one in the area--subscribed ten days of Doxy for Lyme. Because that's just what she does for everything. Which, side note, killed my Red horse and I switched to another vet that doesn't do horses anymore. This woman is the most colossal "old school" pain in the ass and she wants no part of your opinion. So take that into consideration. Sarah is in a tough spot with bouncing ideas off of her vet because the vet won't hear them.

They tried banamine and a steroid. They also discussed treating for EPM, but then Memphis just spontaneously started getting better. I suggested chiro thinking along the lines of something out of whack, but the chiro--who I like a whole lot--didn't find anything alarming.

The vet's summation was that he was just an old horse. Which at the time he was only eighteen. Senior I guess, but hardly some geriatric that was barely getting by with a plethora of other old man symptoms.

The actual hind end twisting, leaning mess only lasted a few weeks, but it seemed to take months for him to regain full strength. For a few months his tail was cocked to the left when moving faster than a walk. Then that seemed to resolve.

A year later, they're at a new barn. A couple weeks ago the whole thing started back up again. He's been normal both times otherwise. No temp, normal heart and respiratory rate.

He's been on Vitamin E for just under a week now as a shot in the dark.

SO.

The fact that's it came back around the same time as last year is weird. The fact that is just went away basically on its own is weird. The fact that he seems like a normal horse in every other way than his hind end trying to fall off his body is weird. Has anyone seen or experienced something similar? Any thoughts on what it might be? We'll take any and all guesses at this point!