What could cause one-direction swing failure on a Bobcat 334 if all other functions are working normally?

[Nicholas Villa]

Trying to troubleshoot my Bobcat 334. It was working fine, then suddenly the swing kept going one way, and now I've got no swing in one direction at all.
All other functions are strong, no visible leaks.
Could this be a swing motor, relief valve, or sticking control valve issue?
Just trying to learn what to check first before replacing parts-any advice appreciated

 

[Gryks Machines]

If a piece of debris is stuck in one or if a spring has broken, the hydraulic fluid will bypass the motor and dump back to the tank instead of moving the machine.