Bathroom odors coming from toilet-to-floor gasket seal?

A friend had a dometic toilet in his new rig. After about a year, he kept smelling foul odor despite how much he cleaned the toilet and surrounding area. He pulled the toilet to find out there was a seal in between the top and bottom half of the toilet frame that was allowing waste to collect inside the toilet frame. It never leaked due to low volume but it always smelled of urine, etc. He got the next model up (i think a dometic 320) and the design was changed and the leak/odor was gone.