If you are having issues with the blade valve on your toilette cassette sticking, one of the simplest solutions is to use a silicon based lubricant on it.

Stay away from vaseline. Vegetable oil can be a good option, but tends to go rancid.

Basic silicon lubricant sprays are available from common hardware stores like Mitre 10, Bunnings, etc – and is handy on a range of other caravan components like window mechanisms and door locks.