I have a similar Bug to report.
I'm also playing on PC. I made it past "carving a pumpkin" and I'm sorry but I don't really recall how it happened or anything about the details of that one.
Mine is further down the Mut Monsters line. The challenge called "It's Alive! It's Alive!"
Very much like yours, your cpu opponent has the ball at the five or so, you have to not allow a touchdown and then go score a touchdown when you get the ball back. I've done it 20+ times now and it fails you either once the CPU kicks the FG, which is allowable by the described rules, or as soon as you return the Kick-Off. You're never given a chance to run an offensive series to score the necessary touchdown.
I bet this is an easy fix for their programmers if they just put somebody's attention on to it.
Good Luck.
Just in case anyone wants to see this in action.
https://www.youtube.com/watch?v=Pdax7_dRLo4&feature=youtu.be
