I don't know but if it were me I would try to bleed the system and see how well that goes. If you find that the system is acting funny then I would replace the slave cylinder, even though it was new, because that is the easiest thing to replace. If no joy is found then replace the master cylinder. I would keep checking for leaks but assume that you would have noticed something by now. After replacing those the next is the clutch fork. When you did the rebuild did you do a new clutch, fork and bearing?
Land Rover 110