Basically, your horse's back muscles have changed again from the original fitting and the secondary fitting. If you were happy with the saddle fitter the 1st & 2nd time then call them again--they should be experienced enough to understand this.
Your horse's muscle will change often, as he develops muscles he had not used and then plateau for a while, then change....
The scenario is .....wash, rinse, repeat.....
Perhaps the saddle is sitting too far over his scapula ?If the shoulder is going back and forth under the saddle it might cause the whole saddle to shift left and right. You could have the girth points moved forward in order to hold the saddle further back off the shoulders maybe? Also a too narrow saddle will slide forward, a too wide one, backwards.
call your fitter out and have her ride in it. if you dont feel comfortable with that, at the very least let her know he's a big side to side mover.
i've ridden them and they are very um interesting to fit.
I have found that developing horses can change substantially in as little as 2-4 weeks! Royal pita for the owner. Especially since a well-fitted saddle that is not pinching seems to encourage faster change!
We had one horse in my barn who came into the barn, and wore a medium tree, within a month, he was into a MW, and he got chunky and went to an XW for a while before he stabilized into a W. My boarder used my collection of saddles on him during changing periods, but still bought 2 saddles in the 3 year period she owned him.
Some horses stay in the same tree size, allowing flocking adjustments to fix them, others don't.
If you were happy with the earlier fit, have the same fitter back out. The saddle fitter can only adjust the saddle, he/she cannot make your horse stay one shape.
He is a very big mover and a lot of movement goes up his back...I've had him for 10 years but this saddle only since November.
what were you using before and did that swing and hurt your hip flexors? (as per your other thread). If you're hurting now, and the saddle is shifting and swinging around now, and didn't for the previous 10 years, then this new saddle probably doesn't fit somehow.
Be sure the panels are even, often used, but sometimes new, panels are unevenly flocked - or if a horse/rider is so uneven a newly flocked saddle can be worn uneven in a very short period of time. Standing up, flip the saddle over, put the seat against your knee, the pommel on your foot and sight down the panels, look to see if they are even. If visibly off, that could be your sliding (fishtailing?) problem. Or the saddle is too wide in the gullet and allowing the back end of the saddle to swing around because its not stable. Or, the saddle is too banana shaped for your horse's back and not making good contact.
Let me say at the outset I'm not a saddle fitter. I have had this happen with a saddle that fits and the problem was the saddle pad/saddle friction and a shedding horse. As I understand it there is motion with the back of saddles. When I looked at exactly where my horse was losing hair it was where the saddle pad rubbed not the saddle. Now that he has lost most of his winter coat the issue is gone. My fix was to use 2 lightweight pads so they rubbed together not one pad and then his skin. You might try it and see if it helps.
The flocking will compress with time, leading to a saddle not fitting exactly the same as it does right after being "tweaked". And I can guarantee you that even horses in the same work at the same level can and will change. I have my saddle fit checked and tweaked minimum four times a year. I had one horse that I had to have the saddle tweaked every 8 weeks or so--he was not developing, he's been at 3rd/4th level for years.
From now on, ponyfixer, i'll include foot note references.
A well fit custom saddle should have uneven panels. It was built to fit your horse! Horses are not totally even on both sides (or extremely few are). They are right side dominant or left, just like we are.
If the saddle comes back to center and sits level when viewed from the back, it is doing its job as it should.
If your horse moves it from side to side it is due to its movement in that it can suddenly move unrestricted. That is a good thing.
The wearing of the hair is that the lower back is swinging. Soreness is not ok, and that means something is still not right yet...
Hip flexor problems I would think are a due to a different position for you, and time for stretches. I had a baby and can relate to the hip flexor stuff. I am in the same boat. My saddles haven't changed though. I did.
I am not saying you had a baby too or had anything change like that for you... I am saying I think you are you are sitting differently, (difference in twist of the saddle, fullness in the upper thigh in the saddle) and stretches would help you.