Too funny!!! I just went thru this. My ball cracked after 5 years full time use.
Two weeks and repair is holding strong. Remove seal, good time to thoroughly clean and apply a layer of Vaseline to bottom side. Clean ball with any cleaner, get surface clean and DRY. One light coat at a time allowing to dry for a couple minutes, Repeat 10 times. My path was about 1/2" wide to create a bandaid effect. Wait a couple hours and replace the seal by simply pushing it into place with the ball closed. Best if water os OFF during this whole repair.
This is more of a Commercial grade SuperGlue, it is GREAT for many things just keep off your fingers!!! Personally would NOT use the homeowner stuff! I have had this for a few years, I keep it in the frig.
Besides this issue this is hands down the BEST RV toilet i have ever owned.
Get er dun!