slight odor from behind thetford aqua magic style II

On that toilet only 2 sources of odor back from black tank....

Does water remain in toilet bowl after flushing. Water needs to stay in bowl to provide vapor barrier....water should not leak out.
If it leaks out.........need to thoroughly clean/scrub seal and ball valve surface

Other place is toilet floor flange gasket......are toilet floor mount bolts tight?


Otherwise....have you removed lower toilet shroud and cleaned. Urine splash/missed...run down behind shroud??