Bench Bleed Master Cyl Question

If the master won't bench bleed, finger-valving the ports, then it's not likely to bleed on the car either.
My guess is the one chamber's compensating port is not open or restricted. The re-sleever should have drilled it out, but only very small. If it's too big, the fluid will just shuttle back and forth from reservoir to chamber. If it it's too small, you will have to wait between strokes, else any air in the bench-bleeding line will act like a big airspring, and fluid transfer into the chamber will be very slow.
Picture a syringe; when you pull fluid into it, the little air bubble at the bottom suddenly becomes a big bubble, as the fluid slowly enters the inlet. Then you flip the syringe upside down and eject the bubble, which has now returned to it's former size. On the next pull, the fluid enters a lil faster and you have to work harder to draw it in... cuz the airspring is gone.
Now drill out the hole in the bottom of the syringe.
And now when you draw in the fluid, it rushes in. The air bubble is still there but it doesn't grow to it's former size.
The M/C and Compensating port work in the same way, except you don't have to upend it to get the air out. But, and this is important, if the piston does not return to it's proper parking spot, then the compensating port does not open, and no fresh fluid can enter the chamber.