what can cause a gear shift to lock up
Also, having a bad fluid pump and a problem on gear selector linkage can also make the gear shift not working properly. Fluid pump is the device that pumps hydraulic fluid inside the transmission to make the gear inside it lubricated and works properly making also the transmission to work.
The shift lock release is generally a button that is built onto the lever. It allows the driver to lock the gear lever into a particular option. For example, when the driver parks the car, he/she can switch the lever into the parking option and lock it there. The lever cannot be moved until the shift lock is released. The shift lock is typically a button on top or on the side of the lever.