MSRS2K

Short Story:
I'm not getting any braking force on my right front. All other corners are fine. When I open up the bleed valve on the caliper and press the brake pedal, no fluid comes out. I disconnected the brake line and fluid poured out of the caliper and line, but I little to no fluid out of the hard line. I was able to suction a bit out of the hard line. The ABS light on the dash comes on when the car is turned on, but then goes off after 2 sec as expected.

How is it possible I'm not getting fluid from the right front hard line when all the other corners are working fine? The situation gets even weirder considering the long story.

Long Story:
The S2000 began pulling left under braking. Checking the rotor temps indicated no braking force on the right front. I suspected a stuck piston and checked the caliper. The boot on the piston was cooked and half gone. I considered a rebuild, but calipers are cheap and just replaced both front calipers (the left was cooked too). Bleeding the left front went fine. Bleeding the right front was a little weird. At first pressure on the brake pedal resulted in a firm pedal and no air/fluid at the bleed valve. But then it started bleeding normally and I didn't think any more of it. Everything went back together and the brakes worked fine. Then a few weeks later it began pulling left again on braking. See short story.

The only think I can imagine is an obstruction in the hard line due to a blockage or the line being damaged. But line damage wouldn't fail, then work, then fail. Also, the line appears fine to the extent I can get to it, and nothing occurred that would damage it. No idea how something could get in the line and cause a blockage. Could it be something in the ABS unit? Thinking my next move is disconnect the hard line at the ABS unit and see if fluid flows freely out the other end of the line. That would probably require a full bleed of all 4 corners and may not tell me anything.

Suggestions? I'm stumped.