I've just tested this with the WTSD filter and it works fine for me.
If you have one that you can recreate consistantly failing, please
enable logging, restart PT3, create and save a new filter you expect not to save properly. Close PT3 down and make a copy of the file:
c:\Program Files\PokerTracker 3\PokerTracker.log
Reboot if that's what you normally do, and run PT3 again, and attempt to open the new filter. Stop PT3 and send both the copy of PokerTracker.log you made above, and the new one, to the
Support system , and link to this thread in the reference field of the ticket so that we can investigate.