need help diagnosing brake issue

[Painter]

Two possibilities-
1- You have to bleed the gauge.
2- If you have moved the attachment point for the brake too far and created too much angle where the push rod enters the mc it will **** the piston and cause this problem.

[Eman]

2) Since I've been swapping lines on the MC, I will thoroughly bleed the brakes again, then as mentioned, remove the lines at the caliper and cap them. Not sure what I will cap them with, but a short flare plug would be great as not to add a lot of air.
Not sure what type lines you have or how they attached to the caliper. If they have flared lines get a line union that fits the flare nut and a plug for the other side. If it's a banjo just use copper washers and a nut and bolt.