I have had this problem too for awhile now...not wanting to lose time leaving it at the dealer. I have an extended warranty (up to 100k miles) but I think I'll do this myself with the beefier part.
One note, in case it hasn't been mentioned before, is that I have found the noise occurs more often if you have the ac/heat off, are using auto mode while cooling, or have the fan blowing to face only mode. So I keep my ac/heat on bilevel or foot level and never hit the auto (or immediately switch to bilevel after auto) to keep the noise from coming on while the motor is on. Unfortunately, this won't stop the noise from coming on 5-10 minutes after ignition is turned off or after the car is unlocked, locked, or SYNC/music is turned on.
This is one reason why this part may be wearing out so quick. This noise will come on even if the ac is turned off. I have no idea why computer is actuating the door so much even when ignition is turned off or you are just listening to SYNC or even after you unlock or lock the car. It seems to be a glitch in the programing but hopefully the beefier actuator lasts longer.
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