If the sensors are malfunctioning, it can cause the garage door to get stuck. One of the sensor lights will typically begin blinking if they aren’t working properly. The first thing to check for is an obstruction in the path of your garage door. If the doorway is clear, then check to see if the sensors are properly aligned. If they are out of alignment, then they can’t see one another and their line of vision is broken. Re-aligning them should result the garage door becoming unstuck if this is the case.
In most cases, only one spring breaks or wears out at a time, and you can get away with replacing just the failed spring. But this is a little like replacing old car tires one at a time. You'll get the best performance if all the springs are new and have the same strength. Extension springs are replaced individually, making it more tempting to replace just one. With torsion springs, you have to disassemble everything to replace either spring, so it makes sense to swap out both springs during the repair.