When I rebuilt mine I had to bleed it for what felt like forever. I think there is just a lot of air space in the cylinder and lines. Try bleeding again. Cracking the banjo at the master really helps but be careful with lots of rags of course. Also, do a check on your fluid level. It's possible the level has dropped some after the first real use. Mine did as well after about a month but no issues since. Whish I knew why. I just assume there was a few air bubbles and the piston and seal shifted slightly with use seating fully in to place.