Lots of missing information, so lots of guesswork.
It is NOT a BMS-related battery shutdown. The error msg proves that. Not because of what it says, but because it EXISTS. BMS shutdown cuts power, there is no error message. Unless you have Canbus or some other protocol, not likely on an Alibaba kit.
Error msg had a RED motor icon. Maybe all error msgs on this display are red, maybe all have a motor icon. No idea, he did not identify any components.
After shutdown, he connects the charger. Then, maybe 2 seconds, 20 minutes, or an hour later, it works. At a low power level. Battery reading at this point is unclear WHEN that reading is reached.
BUT, Before charging, he has to push it to an electrical outlet. So there is a TIME DELAY. How long we do not know. Because the OP did not supply that information.
He did not have this problem when he first got the bike. Likely had it a few months. Likely did not run it as hard when he first got it. We do not know, because the OP did not supply that information.
"Communication failure" Usually means a loose connection or a damaged wire. But, SEVERAL Times, and it comes back reliably, presumably without checking any connections. We do not know, because the OP did not supply that information. However, if power to the motor was cut off, there would be no communication between the motor and controller. 3000 watt motor very likely has a temp sensor. Which communicates DATA to the controller.
A few months ago it was cooler weather. Now the weather is hotter, and in this hotter weather, he is doing 40 mph all the time. Likely many starts and stops, lots of hard acceleration. Typical young kid with a hot rod.
Harder use. Hotter weather. Red motor icon. Time delay to restart. NOT a BMS shutdown.
Very high probability he is experiencing an overheat related shutdown, and there is no problem whatsoever related to the battery.
Delays in communication have greatly contributed to this problem not being positively resolved.
Would have liked to nail this down further, can't trust the OP to answer more than one or two questions at a time, can't trust OP to answer ANY question truthfully or accurately, that plus communication delays VERY aggravating.
Trying to save money on buying 2 36v packs to make a 72v cause its cheaper, you can do it but will not work unless you buy a bms now rated for the packs in series. And when your stuff cuts out usually its heat or controller trying to pull too much amps and your bms went into protect mode.