Mine had the same symptoms, was 6 years old, parts delivery was going to take a few days, dealer made me s sweet deal on a whole new throne, under $125

Took 15 minutes to replace.

In our 9 years of full timing we’ve had several Thetford toilets and the seals always leaked. In each case the RV service company said it’s cheaper to replace the toilet then just the seal because of the labour costs. We now have the Dometic 310 series and the seal can be easily replaced in seconds without removing the toilet. The seal in this unit was defective and started leaking within the first month so I called Dometic and they sent a replacement. It’s now been in for 10 months and has been problem free!

We have the OEM Dometic 310 still 8 years later. I like having the porcelain bowl.
Over the years each time, if the bowl leaked I added some plumbers grease to the seal and it was good again for a long while.
Lately, the sliding plastic door isn't always closing, but we just make sure to give it a good snap back when we hit the flush pedal and all is good. I also find its water shut off valve is getting worn as it tends to leak a little after each flush adding an extra quart sometimes to the bowl
We are due to replace as things are just getting plainly worn out.

Rush change it out for dometic 320. Much better toilet then the thetfod. Thetford is known to leak.
I changed mine out last year no regrets. Mine came with a sprayer which I like a lot. Has porcelain bowl and a real toilet seat not plastic.

We swapped our OEM plastic toilet for the dometic 320 on our previous camper. Nice upgrade.

One thing to look for though is where the water enters from the camper and where it hooks up to the toilet. The OEM and the new Dometic were not the same and required some reworking of the waterline to make a connection. This was awkward to say the least. The old toilet was smaller and the waterline came up through the floor under the new toilet rather than behind it like the OEM. That required drilling a new hole in the floor and relocating the pex elbow in a very tight space under the bathroom floor. What I thought was going to be a very easy install turned into all day, a trip to the hardware store and some scarped up knuckles.

Also before you buy check the clearance to the back wall if it's close on your current toilet. Ours the new toilet was a bout a 1/4 inch off the back wall and barely made it where the stock toilet had plenty of space.

Thanks Guys. Oh well I went and ordered the seals and we will try that once. If not I'll check out the Dometic. Our bowl is a porcelain bowl too. Bottom is plastic. Also it has the sprayer. Thanks as always Men.