I don’t think it was an over-current, I think it might have been motor noise spikes.
As indicated in the last post in this thread:
This driver seems to be fairly susceptible to that sort of thing. I think for now I’ll stick with the SN754410 for this platform, and use one of my new DRV8835 boards in uCee, which has much higher quality (and thus hopefully lower noise) motors.
I will definitely heed the capacitor warning, and make sure I use 0.01 uF caps on the motors.