I think they're synonyms but I'm not sure

ki- = subject prefix for class 7, agreeing with Kikombe.
-me- = perfect tense, indicates a past action with present consequences
-vunj(a) = break (active, as in "I break the window", NOT as in "the window breaks")
-ika = stative (indicates the resultant state of the verb it is attached to when used in the perfect - when used in the present, may indicate the potential for the action to be done to it)

Kikombe kimevunjika. = A/the cup is broken.
Kikombe kinavunjika. = A/the cup is breakable. / The cup breaks (easily, etc.).