Single cell Li-ion battery doesn't charge with PMIC, but does charge without
Solved. As seems to be the norm with me, it was a solder bridge on the SOT-23-6 MOSFETs. They didn't appear shorted upon visual inspection, but I guess it goes to show that you should never assume anything, no matter how many SOT-23-6 you've soldered before!

Thanks to anyone who took a look, and sorry if anyone took any time trying to find a solution to my silly problem.