It won't be a fuse. If a fuse fails the operation won't be intermittent. The fuse protects the wiring. If it fails there is an electrical fault that must be repaired. Just replacing a blown fuse simply yields a new blown fuse.
How many switches are there to open the liftgate? (My 2016 has four; your 2015?) Try each switch and see if any one is reliable. If only one switch is unreliable, that may be your problem. Otherwise the problem may be the electrical part of the latch or the mechanical part of the latch that is activated by the electrics.