I didn't have that issue, but did have an issue with the flush valve breaking. It too is a non-repairable problem. So, I ordered a new toilet, and it arrived broken. The plastic base was shattered. The vendor sent a new toilet, which worked perfectly.
So, I took the new, broken toilet apart to see how it worked. I discovered that these "non-repairable" issues would be very easily repaired if only Dometic would provide the parts. The flush valve could be replaced if only the parts were made available. Same thing with the seal between the bowl and base. Of course, you would have to remove the toilet and disassemble it to do a repair, but it would be worth it if parts were made available.
Mike and Retha Hopkins
2014 40G Fleetwood Discovery