Hey there, hn--ch.
Whenever there are any sort of HDD issues, the first step should always be a data backup (if you haven't done one already), so that you're on the safe side if something unexpected happens.
I'd advise you to try the laptop with a different USB cable (shorter than 12") with the USB 3.0 port again and if possible another computer's USB 3.0 port.
Also, trying another USB 3.0 drive with the problematic USB 3.0 port on your laptop will help you isolate the problem. This way you'll know if it's a USB port problem, HDD issue, or a faulty USB cable.
You could also download a diagnostic tool and test the drive, to see what's the situation.
Hope that helps. Please let me know how everything goes.