The lock mechanism itself is obviously there as an idiot switch--to prevent accidental retraction on the ground (ala Homer Simpson
) If however, it is possible that the microswitch will fail to release the lock as weight comes off wheels. This used to happen to us on one B200 when the weather got down around -40 ish. So we would just pull the release out manually, and continue on our merry way. It seems to me we had a 748 that tended to do the same thing. It just meant that you had to use two hands to pull up the gear.