So long as there is some slack on the cable ands that it's not bound tight by overadjusting then there's something seriously wrong, either the friction plate is not being clamped hard enough between the flywheel and the clutch diaphragm, or there is oil on it, but would have to be literally swimming in it.
I can't see anyway that the arm could be binding, and you'd have noticed if it was.
Who's doing the work, as the principle is very simple friction plate turns gearbox shaft, and is pressed/squashed between the two surfaces, either someting mechanical is stopping that pressure being applied fully, or a dimension is wrong somewhere.
When the flywheel was refaced, they did the WHOLE surface and not just lathed the friction surface, that is to say they took out the dowels that locate the diaphragm and skimmed across the whole lot ?
tabetha