Mobility scooter keeps cutting out.

I have been having problems with a mobility scooter I purchased a while ago. It's a "lightweight Squizz Scooter".
It worked fine for about 10 months, then suddenly, it started having problems. It kept cutting out as it was going along, so that it came to a stand-still. When that happened, the arrow on the charging meter that indicates how much charge is left in the battery, dropped down from full to empty.
We phoned the suppliers, who said it was probably a battery problem, and sent us a new battery. This seemed to work for several months. But just recently, the same problem has started to reoccur of suddenly cutting out without warning, as it is going along.
Usually it is possible to get the scooter running again by taking out the key, and putting it back in. However, this is rather inconvenient in the middle of a zebra crossing!
Has anyone got any ideas of what might be the problem, or any ideas of things to try. It is pretty much unusable in this state
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Sounds like a thermal or overcurrent protection device is actuating.
Difficult to ask delicately, but are you heavy and close to or over the rated capacity of the scooter?
Could also be something binding in one of the axles or whatever serves as a transmission/differential. Does the scooter push easily with no load, and with someone on it?
If you or someone feels comfortable with a little disassembly, does the motor spin freely?
You can also check for something binding by seeing how fast you stop when you coast to a stop without using the brakes.
Dave
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when the unit is turned off the meter is disconnected so it wont drain the battery.

replace the key/switch.

intermittent open is not a normal failure mode for a battery. check the electronics.
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