Shower hard to turn to off position
It sounds like you have something jammed within the cartridge. You can either remove the cartridge and flush line and reinstall it or just buy a new cartridge and replace the old one. The cartridge you need is a number 1222 mowing positive cartridge. Here are instructions to change the cartridge.
MOEN CARTRIDGE REPLACEMENT
There are two different types of Moen cartridge for a single handle valve. The first and most common one is the plastic 1225 cartridge that is used for all Moen single handle valves that are not posi-temp shower valves. This cartridge also comes in brass which is number 1200, but it is more expensive and doesn't last any longer or work any better than the plastic cartridge. The posi temp cartridge is a number 1222. This is the replacement cartridge for shower valves that you turn rather than pull. As you turn the valve it goes from cold to warm to eventually hot. The tools needed for this procedure are pliers, Phillips screwdriver, a small flat screwdriver or awl, a 3/4 inch copper cleaning brush, silicone or heat proof grease, a knife to pull the cap on an acrylic handle, or a 7/64 inch Allen key to remove lever handle.
If it is an acrylic handle simply pry off the cap and unscrew the screw with a Phillips screwdriver. If it is a lever handle there is a set screw which is 7/64 of an inch. Use an Allen key to remove this set screw. If it is a lever handle when the handle is removed you must use a Phillips screwdriver to remove the handle adapter.
Before removing the cartridge make sure that the water is turned off and open the valve to bleed off the pressure. Leave the valve in the open position as it will facilitate the removal of the cartridge if the spindle is in the open position. It can be turned off at the main which is usually the easiest thing to do, or you can remove the faceplate and there may be integral stops behind the faceplate. Use the integral stops if your water main is hard to reach. On the brass spindle of the cartridge there is a notch on one side. Before you remove the cartridge take note of what position this notch is in because that is the position in which the cartridge will be placed. Do not forget this step as a posi temp cartridge will not function properly if installed with the notch in the wrong place. If you install the regular cartridge with the notch in the wrong place, hot and cold will be reversed. Simply remove the handle and spin the spindle 180°.
Pull off the chrome stop tube that encloses the cartridge. There is a horseshoe-shaped retainer clip that must be removed. Use the small screwdriver or all to pry up the top of the retainer clip. A plastic square head removal tool comes with the cartridge that you have purchased. Place this on the cartridge and spend back and forth to loosen the cartridge. Then take your pliers pull the brass spindle straight back towards you. If this proves too difficult and you are unable to pull it out you will have to buy a Moen cartridge pulling tool. Be sure to buy the right tool as they are not interchangeable. The posi temp tool is much fatter than the regular tool. The tool operates the same way a hub puller. Back off the knot on the tool as well as the screw. Place over the cartridge and advance the screw all the way. Now advance the nut.
After the cartridge is removed take the 3/4 inch copper cleaning brush and insert into the cartridge housing while spinning clockwise. When removing the brush also keep spinning it clockwise. After brushing, open the water main for about three seconds to flush the line out.
When installing the cartridge make sure that your notch is aligned properly and that the cartridge is pushed in all the way and that the two tabs on the cartridge are aligned vertically. Install the retainer clip. If it doesn't go in all the way either the cartridge has not been pushed in foreign off or the two tabs are not aligned properly. You can use the plastic tool to align the tabs properly and to help push in the cartridge all the way. Reassemble faceplate and handle and you are done.