Toilets, Sinks, Showers, Tubs and Disposals - failing actuator

I had to replace an old actuator disc. The new one snaps on but every other flush it falls off. Do I buy another actuator disc? glue the actuator to the flush assembly? some other suggestion

If I were you - instead of me advising on what you may or may not be doing, or the condition of the plastic part you have to fit the disc to, why not take the whole plastic piece off and take it to your nearest hardware or big box store - wherever you got the new disc, and show them what is going on to see if you are doing it right or if you need the whole new thing that it goes around.

I have an inkling you are not opening up the groove in the disc properly to get it to engage fully, but could be wrong. [I advised some, afterall. :) ]