A IAI1125 WESTWIND IN CRUISE AT FL410 DIVERTED DUE TO ABNORMAL AILERON CTL.

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WE WERE EASTBOUND AT FL410 IN CRUISE FLT (CENTER GRANTED 'WRONG WAY' ALTITUDE) WITH THE AUTOPLT ON. THE CAPT WAS PREPARING A CUP OF COFFEE AS THE AUTOPLT BEGAN A SERIES OF UNCOMMANDED HEADING CHANGES. I ASKED TO HAND FLY THE AIRPLANE AND TURNED THE AUTOPLT OFF. I IMMEDIATELY REALIZED THAT ROLL CTL WAS ABNORMAL. THE AILERON CTL FORCES WERE VERY HIGH AND PRODUCED A 'STICKY' OR 'RACHETY' FEEL. I ADVISED THE CAPT AND HE TOOK THE CTLS; AGREEING WITH ME ABOUT THE ABNORMAL AILERON SIT. WE ASKED FOR DSCNT TO FL 370 AND REVIEWED PROCS FOR THIS SIT. THE PROB REMAINED SO WE ADVISED ATC THAT WE WISHED TO MAKE A PRECAUTIONARY LNDG AT ZZZ AND WERE DSNDED AND VECTORED TO DO SO. PASSING INTO WARMER AIR AT ABOUT 15000 MSL THE AILERONS BEGAN TO REACT NORMALLY AND WE MADE A NORMAL LNDG. AN OUT OF SPECIFICATION AILERON CTL ROD LATERAL BEARING WAS FOUND AND REPLACED. ALSO; THE ACFT HAD SAT IN THE RAIN AT ZZZ1; FO. THE TWO PREVIOUS DAYS AND THERE WAS SOME SPECULATION THAT MOISTURE MAY HAVE REACHED INTO THE SYSTEM AND FROZEN AT ALTITUDE; ALTHOUGH NONE WAS OBSERVED DURING THE INSPECTION. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE AIRPLANE WAS PARKED FOR TWO DAYS IN HEAVY RAIN AND WATER HAD PENETRATED THE WING LEADING EDGE WHERE ALL THE AILERON CTL COMPONENTS WERE LOCATED. THE RPTR SAID THE WING LEADING EDGE WAS FOUND TO BE POORLY SEALED AND REQUIRED SEALING WORK TO PREVENT WATER SOAKING. THE RPTR STATED A CTL ROD BEARING WAS OUT OF LIMITS AND REPLACED AND ONE AILERON ACTUATOR WAS FOUND RUBBING ON AN ACCESS PLATE SCREW. THE RPTR SAID THE ACTUATOR ACCESS PLATES HAVE THREE DIFFERENT LENGTH FASTENERS AND THE ONE LONG SCREW WAS INSTALLED IMPROPERLY. THE RPTR STATED IT IS BELIEVED THE MAIN CAUSE OF THE ABNORMAL AILERONS WAS FREEZING OF THE AILERON COMPONENTS DUE TO WATER PENETRATION.