This doorknob when locked spins either direction without opening. When unlocked, it used to work like a normal doorknob but now will only turn counterclockwise. Is there an easy way to fix this so it can again be turned either way to open the door?
If it would previously turn either direction and now does not , this is indicative of either something physically blocking the mechanism inside or needing lubricant. Either way your solution is the same- disassemble and lubricate. Remove the knobs, then remove the latch assembly. Remove any obvious pieces of metal or debris that are present, add a lubricant, work the mechanism, and reassemble.
Disassemble the door knobs from door. Leaving the latch in place determine if the latch moves in both directions (CW and CCW) and returns to center. If not, determine what is causing the interference or "drag." Lubricate as needed.
Holding the knob that interfaces with the latch in your hand, verify the knob turns in both directions and returns to center. If not, determine what is causing the interference or "drag." Lubricate as needed.
Finally holding the other knob in your hand, verify the knob turns in both directions and returns to center. If the knob only turns in one direction, then one of the rotational stops has likely slipped past the end of the torsional spring. (The torsional spring ends limit the rotation of the knob). Both stops need to be on the same side (wider space) of the spring ends. Push the spring end down and rotate knob to allow the stop to slip over the spring end. Push that spring end back up to capture the stop.
Reassemble knob and verify door knob functions properly.