It's very unlikely to be the PCB, more like firmware and/or media issues. Although you could try a USB 2 cable, with the smaller connection.
If the data isn't that important and you're willing to take the risks of DIY (not easy due to SATA conversion, firmware repair, imaging around bad sectors, encryption etc..), then there are some threads on here that may help. Search "slow responding" for starters.
Otherwise if the data IS important then send to a data recovery company, it shouldn't be too expensive AT THIS STAGE but could easily get a lot worse very quickly if you play with it too much!
Good luck!
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