I'm still pretty new to here and to the camper life in general. But, I had my toilet spring a leak behind it. It appears to be the vacuum breaker. The unit is still practically new. 2017 Wildwood X-Lite 273 QBXL with 300 series dometic toilet. Anyone else having this issue on one so new?
If it's the vacuum breaker it is held in place by a rubber grommet (seal) at the back of the toilet. You might push on the back of the breaker to see if it will go in farther. The breaker is removed by just pulling on it straight back. If the leak is from the plastic breaker itself it will probably have to be replaced but it is inexpensive.
The age of the unit is probably not as important as the water pressure at your site. If you weren't using a good water pressure regulation, you might have damaged the vacuum breaker. Ask me how I know. I sent an email to Dometic and they sent me a new vacuum breaker free of charge.