Need to get more information before posting on this - thanks.
Flex Tree/Treeless saddles always have the risk of creating a band of pressure where the tree “breaks” on a flex tree saddle, or underneath the rider in a treeless saddle. The function of a wooden tree is to distribute weight. When you take that away, you end up with more concentrated pressure on a smaller surface area.
Personally, I do not like flex tree or treeless saddles for this reason.
Before I go any further, I’d want to know what the make, model and year the saddle was made and see a photo of it on your horse.
I know nothing about treeless or flextree saddles, but if your horse is improving and muscles changing, the saddle must change as well. Adjustments or new saddle to fit.
I had my conventional saddle checked and flocked every 6 to 8 months.
Another thing that can be an issue if the rider gains or looses a lot of weight,. This alters the true position in the saddle, but usually the rider feels it.
If the saddle is slipping forward, then it does not truly fit
