Front driver side brakes locking up

every time i press my brake pedal, even lightly, the front caliper on my driver side won’t release. I’ve replaced both the caliper and the master cylinder. last time i replace the pads, i wasn’t able to reset the cylinder at all and had to replace the caliper again (thank God for warranties). i haven’t had problems with any of the other brakes on the van. what could be causing this problem?

The inner lining of the brake line to the cylinder may be collapsing. Change the line.

Your brake hose is restricted. Replace it, and consider replacing the other front one as well, before it starts giving you problems too.