Unfortunately, this is a problem with a lot of different potential causes.
Perhaps there’s a fault somewhere in the motor. Perhaps there’s a leak, and the water is getting where the power should be. Perhaps the motor overheats when the machine gets overloaded (this is probably what was happening to mine, which is why I replaced it with a front loader).
Of course, you can also avoid the problem by just not overloading the machine. But if your family has too much laundry for the machine to manage, it may be worth thinking about an upgrade to something a bit bigger.
If the problem persists, it's best to call the manufacturer to discuss repair.