Fought with it on the weekend. I'm not sure if I did it right, but I landed up in each side of the proof assuming the negation of the consequent and then using the rules to introduce a contradiction. No idea if that's the right approach but didn't know what else to try...
I tried a few things on the weekend, even sent an email to the lecturers asking for some assistance.
I tried to assume ~K1(p & q) but not sure what to do with the ~K1 once it's in the box.