Welcome, @DinguRingu!
I'd strongly recommend you backup as much of your data as you can from the hard drive somewhere else before proceeding with the troubleshooting. Better safe than sorry, right?! Afterwards, try swapping the SATA cable and the port where the drive is connected to the motherboard. Once you do that, check the health and SMART status using
the manufacturer's brand-specific diagnostic tool. If you have access to another PC, you could also try plugging the HDD there to see how it will perform.
Keep me posted with the troubleshooting!
SuperSoph_WD