I am not an expert, but have done my own pedal pivot, master cyl, slave cyl, and clutch replacement. I would recommend making sure that all the components are adjusted/installed correctly. In particular since you remarked that you had your pedal pivot rebuilt. My Previous owner had this done incorrectly instead of replacing it, and it took me a long time to realize that the pivot was incorrectly welded. 1st make sure you have 134mm
from the pedal pivot to the Clutch master cyl. See picture (red Line)
Heres the diagram from the manual
I would also check the condition of the flex line to the slave cyl. you may have a weak rubber flex line and be losing pressure if the line is ballooning out when you press down on the pedal.
Good luck and let me know what you find