'04 Impreza Outback Sport 2.5L EJ251 (not positive on engine style) Clutch line issue
Currently dealing with a weird situation with my clutch.
Initial context: Bought the car from a younger kid, he had done a ton of work to the car including completely overhauling the clutch line and cylinder components. A few months of driving later, the car started having issues with the clutch coming only halfway up after pushing it in. After some initial research, I tried bleeding it with no luck. It should be noted that bleeding was incredibly unsatisfactory despite full compression of the slave cylinder. I decided since some fluid was coming out of the slave cylinder, that it could be that, so I replaced it and tried bleeding again. Both times, bleeding felt significantly less productive than I expected from my limited experience bleeding brakes. The second time, I was shocked how much black gunk had collected in the reservoir after cleaning it and adding new fluid the first time. The issue has not really gotten any worse since the second attempt at bleeding after replacing the slave.
Main question: I feel that this may be because one of the lines he installed was not rated for brake fluid or perhaps from the master cylinder going bad early. Does one option here seem more likely than the other or am I missing any other possibilities? Thanks for the help