Why are my front brakes locking up & how can i fix this?

Has it got a weight load sensing valve this evens the brake force between front and rear brakes

It's either brake fluid hose or caliper itself, see if caliper piston is easy to push back in, if yes, replace the hose, if not replace the caliper,

If the Mechanic on the job could not find out after working on it ? Brake Pads sound easy to fit , but they are not, if they dont go in 100% flat , problems. Another big problem, use GENUINE PADS, as fitted by manufacture, Afer market , unknown Pads not good.

The fact that the service 4wd light comes on is good. That gives us something to go on. Did you have the 4wd trouble codes retreaved? If you tell us what the codes are we can go from there

The hose could be collapsed internally holding residual pressure and keping the pads applied. Also make sure that the caliper is sliding free side to side.

it could be a flex hose between the caliper and the steel line

FRONT ROTORS WORN OUT.IF ABS AND AWD NOT WORKING THE DEALERSHIP HAS TO FIX.BECAUSE THEY HAVE TO USE DIAGNOSTIC EQUIPMENT TO TROUBLESHOOT AND FIX.

your brake calipers are stuck! replace the brake calpiers and won't hurt to replace the hoses at the same time.

The piston is binding in the wheel brake cylinder, perhaps a bit of rust in the cylinder.
Inspect it, replace wheel brake piston and maybe the cylinder if you can't make it "smooth".

It is most likely a bad front wheel speed sensor.Your sure abs rings were on back of rotors?It is going to be next to impossible to fix without getting the code with a scanner