Chrome one-handle tub filler includes hand shower

I bought this product in January, 2021 as part of a bathroom remodel. It has not, to this day, ever worked correctly. Specifically, the diverter valve that redirects water to the hand shower does not fully reset when the water is turned off. So when we turn the water back on, some water comes out of the faucet, and some out of the hand shower. We have had 3 different plumbers attempt to fix it, and none have found a way to make it work. One of them replaced the entire diverter assembly, and it still sticks. I called the Moen Customer Service number and told them my story. The woman I spoke to offered to send me yet another diverter assembly, and the instructions on how to change it myself. I told her that a complete replacement of the diverter assembly has already been done, but that was to no avail. Sending me yet another diverter assembly was the only option she would offer. She reminded me of how expensive this item is, and that I certainly shouldn't expect Moen to bear the cost of replacing it until I at least tried replacing just the diverter again. So I gave her my mailing info, and waited for the new diverter to arrive. When it arrived, there were no instructions included. None. I have no idea how to install the thing, and I certainly don't want to risk damaging the unit further, having been chastised about its expense earlier. At this point, I'll pay a plumber to come out and install the new diverter. If it works, fine. At least I won't ever have to deal with Moen again. If not, I guess I'll call customer service again and see what they're willing to do, if anything.