[MarkJames]

I have a real problem with a shower cartridge leaking. It seems to be Moen Posi-Temp Faucet
Model 1222. I say it seems to be. Because the one I took out was not easy.
Even with a puller tool, It broke off. So I had to get it out in small pieces.
I cleaned out the hole making sure their was no more debris in it.
Bought a new Moen 1222 from Lowes. When I tried to fit it in, I found it was 1/16 inch to long?
I found this out after removing all seals, so that it would slide in easy. There is no way I was able to get the clip in? I have replaced many cartridges in the past, mostly 1225's. And never came across one like this? I had an old Danco 1222 & filed the back of it down 1/16 inch. It went it easy & I could get the clip on with ease. So I went back to Lowes to buy a new Danco 1222. Filed the back of it down. (You can't file down a Moen, their's has no room on the end, because the valve is right at the end) Fitted it in & turned the water back on, to find it still drips? I pull it out again to check the seals are in the right place, they were. So put it back in, to try again & still it leaks? I just don't know what to do next.
Why did I need to file it down to fit?
And why is the new cartridge leaking?

I never had one break. And I never had to modify one - that just sounds wrong. If it's Moen, the trim plate will say so. Look carefully. Sometimes you have to push the body that extra little bit. Instead of removing the gaskets, lube it with plumber's grease first. Did you have calcium deposits or something in the valve body? Inspect with flashlight and see how clean it is.

Edit: Ugh, if you took it out in pieces, maybe you scratched the inner surface - not good.