Don't throw that Xiaomi Powerbank 5000 yet...

If you have a Xiaomi Powerbank 5000 and find that it keeps flashing the full LEDs when charging but when discharging to a device, it instead flashes one LED, then it could be the wire for the temperature sensor has broken off the circuit board.

Open up the powerbank on the non USB port side with a blade and screwdriver then slide it out at the opposite end. You may find that the one or both of the two wires connected from the battery to the circuit board may be disconnected from its solder point. Solder them back then test it. If it works then put it back together.

This video shows where the wires are: