Is there a contradiction in the translation of the Bhūmija Sutta?
There's no such contradiction. Karma can indeed be categorised as prompted and unprompted as in if it was instigated by another or not.

What's refuted here is a person or a third party being able to create pain, pleasure or neutral feelings at will. Feelings arise due to contact.

Ex: One cannot say "let there be pleasurable feeling at the ear" and make it arise, if there's no contact at the ear. Even if one performs the physical act of playing a song, if one is deaf, pleasurable hearing won't arise since there's no contact.