Hello, I hope the following is of assistance.
By far the most common concern that blows fuses or gives locking/unlocking problems on this model is damaged wiring in the rear door.
The wiring to the rear door runs through a plastic tube, with the constant opening and closing of the door eventually the tube or wiring becomes damaged enough to cause a short or open circuit to the rear door lock motor.
Remove the driver's rear door panel inside and inspect the wiring, if you need to replace the wiring the loom to the door plugs in next to the rear lamp, if you remove the lamp you'll see the connector, the wiring from the connector is usually all black for security reasons.
If this wiring shorts to the door then this can blow the locking fuse, if the wiring to the door motor is an open circuit then you can end up being unable to unlock the rear door.
Start with checking this, as I mentioned earlier it is a very common problem.
Let me know if I can assist further or if you have more questions regarding this and I'll reply as soon as I'm able to.