Need help debugging ebike: Laggy motor / inconsistent behavior
The unusual bursts / full blast behavior could be related to your cadence sensor at the bottom bracket. Depending on the type, it could be related to water ingress  / corrosion to the sensing contacts, causing false pedaling to be registered. Also makes sense if it happens around rainy days as water might affect the sensing.

Do you have a throttle you can use to isolate the problem?