Clutch bleeding issues. Stock master cylinder faulty?

[NZZL1]

Tilton ST-246 organic clutch, Tilton 60-6107 hydraulic release bearing with remote bleeder. Operation has been good for 20,000 miles, but the clutch is now slipping when loaded. A bore scope camera suggests that there is sufficient friction disc material, and that the hydraulic release bearing has sufficient travel.

I was not getting consistent flow with bleeding via 10 feet of hose into a high-mounted remote catch bottle, but this "partial" bleed did lower the clutch engagement point on the pedal and there was no more slipping (initially). With a little more driving, the clutch engagement point on the pedal has since moved a little higher, and the clutch is now slipping again.

Bleeding was odd, in not getting a consistent flow initially, and then no flow at all. I am theorising that the bypass/transfer port in the master cylinder is blocked and that there is too much fluid in the system, causing the hydraulic release bearing to not retract fully. Is this possible, or does anyone have any better ideas or experience?

[fz4k98]

The clutch master cylinder makes sense and is the easiest to try to replace. I had a bad one but it would cause pedal engagement to move downward after a bleed and driving for a while.