Sullom Voe to Aberdeen in a Bell 214ST just after the Piper Alpha disaster, so 1988. About 10 minutes after take off the cyclic was found to have jammed in roll with about 3 degrees roll movement to starboard and 5 degrees to port. Diverted to Wick with all turns to the right so we could pick the bank up with the greater movement of the left cyclic. Did a running landing. On restart after an engineer arrived from Aberdeen the fault had disappeared. After all this time my memory deserts me as to what the possible causes were.
Also back in the 70's on a Bo105D the hinged cyclic lock arm fell down and briefly locked the cyclic.