As stated above, I think it is highly recommended to replace both master and slave when one unit fails.
I had an issue getting my clutch properly bled until finally "reverse bleeding" as Bill Boudreaux outlines on his ZFDOC website.
http://www.zfdoc.com/clutch_hydraulic.htm
https://www.youtube.com/watch?v=P9SiMPuFa00&t=263s