that damn intcode computer from last year is still giving me PTSD. Had a bug in it that somehow didn't show up in the first three challenges, took me forever to find.
I had one of the funniest bugs in my whole programming life with intcode. It manifested itself in the last puzzle (iirc) with the maze. I did not find a single item, because the instruction used for this was buggy and the rest of the problem was 100% ok.