Yeah 3.925V per cell resting suggests around 60% is left in the pack, no issue with run time.

Do you have any way to test the pack's IR (Internal Resistance), as some chargers can do? Or try a different pack, perhaps a buddy will let you do a run? If the pack is getting tired it wouldn't be holding voltage under load as well, could be contributing.

If the pack is good, here's something to try. Refer to the sample discharge graph of a good cell, note a fair bit of drop off early. Don't charge the pack all the way. Some chargers have adjustable cutoff, I use a Hyperion that has a percentage cutoff feature for example. Some have a fast charge mode, etc. Or just try stopping soon after the CV portion starts where the charge amps begin dropping off.