I had the same issue. What I did (which seemed to work) was to create a separate K-1 entry for each entity (my K-1 also had a supplemental 199A attachment that included two additional entities). I created a K-1 entity for each entity to enter the supplemental 199A information which was just the box 20 information.
Not sure if this is your fact pattern but, if so, hope it works for you.
