What length arrow are you shooting? Inserts? Draw length? Fast flight or B50? Shelf or elevated rest? How much left are we talking about -- feet or inches?
Bareshaft dropping at last minute is probably nock high -- though it could bounce off the riser (nock low). I usually tolerate some nock high as long as it's minimal.
I resolved to never make any assumptions until I have 3 consecutive days of consistent data and about 50 serious arrows downrange per day. The overall trend will reveal itself over time. But any individual day could be nothing more than statistical noise.
Sometimes, it's not even worth messing with. Yesterday, I noticed that my arrows were grouping right about 8-9" at 25 yards. They flew perfectly and consistently (10" group -- good for me at that range with no clicker and opposite hand) but just off a bit. This was a new combo of wood shafts from a selfbow and 30# limbs for my recurve. Rather than mess with length, tip weight, etc., I just held the nock ever so slightly askew of my eye and it corrected right out. Backed up to 30 yards & still on-target. Problem solved.