If the tires on front are a different size than the tires on rear,,, would that cause the brakes to lock down without applying the brake?

SOURCE: 1996 jeep grand cherokee, quadra

Since you aready paid $400, go back to ;the shop and get your $'S worth!! Unless someone can prove that the axle bgs were bad, you shoulld ask why pinion & side gears were not diagonsed!!! (dosen't anyone test drive stuff after they "fix" something anymore??? Dosen't anyone give a damn???
If you can't get anywhere with this, find a junkyard unit and install it yourself. It isn't that hard. Just be sure that new lone has the same mount points and gear ratio matches ratio lof front axle.(count gear teeth if you must)

SOURCE: turn signals blinking fast and stop when brakes applied

likely not, but change /check anyhow....If problem persists, likely you will need to change the module that controls directionals (usually under dash to the right of steering column)

SOURCE: front end vibrates when brakes are applied

Sounds like the rotors are warped,Were they checked during brake replacement?

SOURCE: When appling brakes on a 2000 Jeep Grand Cherokee, steeing wheel

New revised calipers. and have the new rotors machined right out of the box before installing

SOURCE: 2002 Jeep Grand Cherokee Laredo 4.0L front passenger brake sticks

First you must look closely at the caliper and determine if it is sticking on the slide or is the piston sticking. If it is the piston you would have to rebuild the caliper or replace the caliper. If it is the slides, you need to sand and clean all the slide contacts and lube the slide with lithium grease or never seize grease. Then you can reinstall the caliper and you will be fine. Also when checking if the piston is sticking try loosening the line and see if it retracts, if it does you may have a bad flex hose going to the caliper holding pressure on the caliper.