Brakes

Pull the wheels and have a look at what’s going on. Might need pads, although that usually creates a grinding sound and doesn’t cause wheels to lock up. Might be a fluid leak which can make brakes grab. A seized caliber or slave cylinder could be forcing all the brake pressure to the opposite wheel causing it to grab. Check it out so you know what to expect if you take it to a shop. Don’t let them oversell you. They love to do the whole meal deal which might be overkill on an old car. Daughter in law was quoted $1500. I fixed her up for $40 and had 2 pads left over.

It has new pads and calipers. Could it be master cylinder?

If they were working fine before you did the pads and calipers then its likely related to that.Are the rotors in good shape? Did you bleed the calipers properly and then bleed the front brake lines after you put them on. Did you relieve pressure on the ABS system before doing that work. I believe it calls for rapid pumping of the brake pedal before opening up the system. I'm not sure what happens if you don't follow these steps, but it could affect the proportioning valve and/or how the abs system works. Just tossing out ideas here.