There were some Acer laptops that were poorly designed and had premature failure of the USB ports on the back of the laptop.
They would start by partially working and end up not working at all.
But as far as I can remember, no recall for that problem was ever done.
So sometimes it is not just a matter of dirty connectors.
It is instead a matter of USB ports that were not supported well having the connections to the motherboard fracture and either stop working or working intermittently.