The final cut of TMC Podcast #29 is available now with topics time-stamped. We discussed the Tesla Cybertruck's expected 1 MW Ultra-Fast Charging capability, the Tesla Semi Delivery Event, the coming Model 3 refresh (project "Highland"), and more. You can watch it now on YouTube.
Yes, the exact 3/4 of the normal current shows what this issue is. It doesn't have to do with v10 software, though. That would just be a coincidence. When ramping up the current, the car looks for a large amount of voltage drop, which might indicate a bad/loose connection in the circuit that could create a dangerous hot spot, fire, etc. So if the car sees too much voltage drop, it will cut to 3/4 of the regular current level and see if the voltage level is stable enough, which it usually is. There was probably some voltage sag for some reason that may even be related to some random dip in your neighborhood connections that affected multiple houses. You are welcome to go on the charging screen in the car and turn the amps back up to 40. If it does it another time or two, though, you should probably check the wiring connections in the circuit to make sure you don't have a problem there. Or, you could also not go quite as high with the amps. If you go in the mid-30's, it will probably not trigger that safety lowering and is still faster than 30. I generally recommend against using 40A all the time with those gen1 mobile connectors anyway, as they do get pretty hot at that maximum level. I've been running more like 31-32 amps for 5+ years to help the long term life of my cable.