My RX 570 is doing a clicking noise!

It is a refurbished XFX RX 570 that was used for 1~2 years, I don't exactly know what it was used for though

 

Does the card use XFX's "hard swap fan" system? If so, replace the fan.

From your description, it sounds like bearing failure. Failing bearings don't always get louder with speed and in some cases, can be quieted by changing orientation because it changes how the bearing is contacted.

 

I think when you lay the computer on its side gravity is no longer pulling the fans down as they are floating/spinning sideways.check and see if there's any in-and-out movement on your fan...also one of the fans could be offset just a tad to

 

Assuming nothing is making contact with the fans then re-seating the card is the only other thing you can try.
So pop the card back in make sure its in securely and see if it does it again.

https://www.google.com/amp/s/basic-tutorials.de/en/what-is-coil-whine-and-how-can-it-be-fixed/amp/