I’ve had this in some of my courses, normally it’s because I’ve had another entry which translated to the alternative I tried to select, ie the selection was actually an entirely different translation pair for memrise. to illustrate:
word A -> Translation A (Alternative B)
word B -> Translation B
In the tapping test I’m asked for word A, and am offered Translation A and Translation B. Picking the latter is marked as wrong, as Memrise sees this as a different translation, it does not offer Alternatives in tapping tests.
I’ve had to clean up/clarify a few entries over the years…