Waste,
Don't glue it in? You have to be kidding. With the pressure on this thing from the top part of the valve you will get some 'sticking' and it will lift right out of the channel first time you go to change positions. If that doesn't happen then the first time you go to change positions with any flow whatsoever it will get displaced and ruined. The flow could be simply the slight flow that is the result of opening the waste port that is usually open to air. As for getting a glued one back out....scrape it with a small flat blade screwdriver or something similar that fits in the channel.
Al