old interior door knob can't turn
WD-40 is not a lubricant which is why it's only lasting a short time.
Use something to clean it out, carb and choke cleaner is reasonable and follow that with some compressed air.
Then apply some graphite-based lock lube to the moving parts.  These are also often called &quot;dry&quot; lube and they don't hold dust like oil-based lubes can.
Once it all moves freely with the new lube, you should be good to go.