When you refer to the shaft holder are you talking about the round motor block door ?
its the round wheel like part that seals the end of the motor block and holds one of the bearings for the magnet shaft inside the motor block housing ??
If so using pliers will damage the motor block door.
If using a sturdy marker cap does not help you then you can give a stern push on the motor block to get the assembly to move.
Make sure to use something like a butcher block and KEEP THE SHAFT STRAIGHT so you do not side load it because side loading will break it.
most times when taking mine apart I hold the motor block in my fist and give it a straight down tap onto my butcher block cutting board, The shaft will push into the motor block causing the magnet to push the ''cage door'' up and outward.
A small screw driver that is no longer good is used (handle Part) to keep the shaft depressed and tight against the assembly to push the shaft all the way against the motor block and finishes pushing the cage door out.
After removal of the door simply pull the magnet shaft out for cleaning.
Make sure NOT to install this cage door until AFTER you have reinserted the Magnet shaft assembly.
If for some reason you think there may be a good amount of build up of organic sludge or Calcium carbonate built up in the pumps motor block causing it to be excessively tight then soak it in a vinegar solution before hand.
A small handle screw driver can be had for cheap at a local store. You can cut, grind or file the handle end flat which will help keep things straight and not sliding on the factory rounded surface.
The pointed end or flat end can be cut off flat, I use a small piece of scrap wood on the table to keep the metal end of the screw driver from digging into my table (wife appreciates this part )
This has been more sturdy for me VS using a marker cap.
