Also,
I AM A DUMBASS.
Ahem.... *clears throat* Excuse me. I apologize.
Soooooo yeah of COURSE it won't transfer. The next file on the list is one of those large-ass PDF files, and it's 242 MiB while my free space is only 194.2 MiB.
Which leads me to wonder............
HOW DID I NOT REALIZE THIS BEFORE?? 
Ugh, I feel so silly... I am SO sorry to have wasted everyone's time here...