It is pretty much always the motor unit problem, no amount of lubrication is going to help. I had this problem with both mirrors. Good thing is that you can buy the motors from aliexpress:
https://www.aliexpress.com/item/1005006 ... 180225ZVsC
It is best to buy the whole actuator unit.
The quality is actually very good but the replacement is a bit of a struggle. The mirror can be fully dismantled, be careful with plastic clips though and it may take some time to figure it out. The hardest part is to remove the spring, you have to push the plate down and twist, it is a hard one. I managed to do it with long tip pliers. Also the wires tend not to fit through the hole of the motor with the rubber boot on. Basically the boot can be removed cutting half way through, it will seal sufficiently afterwards, there is no direct contact with water anyway. All and all it is doable and for the cost absolutely worth the effort.