The only thing I can think of is that the entire unit, including the compressor is getting too cold to function inside that contraption.
I know spfoam1 did a best air temp of -15c in a similar setup that blew -15c air into his sealed pc case.
I've been down the road, it was fun as hell tinkering with it all every day and tweaking till I found absolute best case scenario in efficiency and setup. But, I must say, once you go Ln2/Dice Pot action, you never look back except to say "Man, I wish I skipped that whole chiller phase I went thru"
