Hello,
To begin I have a 1988 740 turbo wagon. The cars front brake calipers are bendix. While driving the other day the wheel starting shaking and when i pulled over the front driver side rotor was very very hot. So I got to inspecting the problem and the brake pads are locking up on the rotor. I have just put on new calipers about 500 miles ago , drivers and passenger side. While inspecting the caliper I noticed that all seems good, the pistons are not seized and the guide pins are moving very freely. I cannot figure out why the caliper will not let go of the rotor. Any advice is welcome and apprectiated. I have heard that a bad broke hose to the caliper can cause this, is replacing that an option? or should I be looking elsewere.
Thank you for any help.

Yep the rubber brake line can suffer failure of the inner lining which allows pressure to be applied to caliper but not properly allow pressure to dissipate.
Remove and replace hose. 10$. Can be difficult to separate from hard line and/or caliper. Spray ahead of time and let sit. A good 11mm flare wrench(Snap on) helps.