When I bought my 4Runner the guy had improperly installed the right hub, when installing you must make sure it is in the open position and that the spring is fully retracted and locked. Don't know if this may be your issue, compare the one that is sticking to the one that is working. If the inside of the hub is retracted that is the open position, if it is not retracted and it says it is open it will hang up and stay locked even though the hub says it is open.
