I also had a problem printing this. Same issue as reported here, the cap's hook has nothing to latch onto within the divider core itself. Also, the core printed perfectly, up until the top 1cm where the wall thickness mysteriously went from 2 to 1 layers thick and went wacky. There is something odd about that top section of the core. It slices fine and the STL looks fine when viewing, but something up at the top is preventing a nice print. Very strange indeed.
Otherwise, this is a great little divider and I would use it very frequently if I could get that top section to print properly. Looking forward to other's suggestions/comments.