This does not sound easy.
It might be time for a new valve.
I attempted to remove a square drive diverter seat with a stepped
seat removal tool and the end broke off inside the seat.
I thought I had inserted it up to the correct size (one size too small) and twisted it off.
The end of the removal tool is stuck inside the seat.
Any ideas on how to remove? I tried drilling but the metal appears
to hard. Maybe a special drill bit?
Thanks in advance.