The issue is the wiring loom which splits off for the coms protocol for the lower battery mount.
I have found that reducing any movement of that cable whilst riding hard, can mitigate the problem for turning the bike on.
The battery itself is fine, as well as the motor. It's simply that wiring loom.
View attachment 145978
Dengfu had the same problem. They redesigned the lower mount for a better interface for the battery. But the bms trigger switch still posed a problem with hard aggressive riding. Hence, why they ditched it for a different mounting design for the battery for the E55 & E82.