Dual battery packs with internal BMS

I have to 72 volt lithium ion battery packs each with its own internal BMS. They are hooked in parallel. The rated cutoff is 56.9 volts. Today they cut off at 69 volts. I have ridden at 65 volts and still had juice left. Is it possible that one pack was low enough to cut off causing the entire system to stop even though 1 pack had enough juice to register at 69 volts? If this is so would it be better to fix some sort of switch to switch between the two batteries and run out one at a time? Any advice would be greatly appreciated

rule 1: thou shall check voltages.

pull the battery open and measure each cell group. see if the voltages are the same.

There are several possibilities. First, what is the capacity of the packs and how many amps are you drawing?

If one cell in the pack goes low, it will cut off even though the overall pack voltage still looks OK.
If one pack cuts off, all the load shifts to the other pack, which may or may not be able to handle the amps.