I had to pound in the last 1225 moen cartridge,after that it took 2 weeks to leak

I had to pound in the last 1225 moen cartridge,Please explain why you had to "pound" it in. We remove the cartridge and turn the water on for a minute to flush out the supply and the open valve body. Good luck, Tom

When installing a cartridge, do it with the stem in the open position. That is with the stem pulled out. If the stem is closed you have to compress all the air and water that is trapped between the valve body and the cartridge. Having the stem pulled out lets the air escape.