My vehicle:
1985 300CD-T (Calif.), W123.153

Issue:
Driving on the freeway, I smelled what I believed to be a "burning brake" odor. In attempting to slow down, I felt two bumps through the brake pedal as I was applying moderate pressure and the pedal was moving toward the floor. Stopped, I determined that my vehicle was the source of the odor. The odor appeared to be coming from the front left wheel.

I inspected under the hood and under the vehicle. No obvious signs of damage or leaking fluids either on the ground or vehicle. Fluid reservoirs appeared full.

With the front end of the vehicle off the ground, I attempt to manually spin the left wheel. It was far harder to spin than the right wheel.
I removed the front left wheel. No signs of anything amiss.

I removed the outer brake pad. All appeared okay. I carefully and slowly pressed the piston into the caliper as I would do as part of the job of replacing brake pads. All appeared okay.

I experienced great difficulty attempting to remove the inside brake pad. It seemed greatly hung up. Eventually, I was able to remove it. I carefully and slowly attempted to press the piston into the caliper. It would not (or barely) move.

I cleaned the caliper, re-installed both pads, and went for a drive. Once again, I felt two bumps through the brake pedal as I applied moderate pressure and the pedal was moving toward the floor. I am no longer smelling the odor.

As for the front brake calipers:
Bendix installed by an independent technician in May of 2000
88,246 miles on them

Question: Does this seem to be a matter of a failing caliper (as I believe)?

Thanks for any insight and advice with this situation.