When nothing is attached to the brake pedal, does it swing freely?
Was this problem present with the old master cylinder?
When you bench bled the new master, did the plunger return freely?

You could have a brake pedal pivot issue.
You could have a new master cylinder problem.
You could have a linkage binding issue. You need to test each possibility on its own.

When you step on the pedal, your foot pressure overcomes the problem, but when it returns, it relies on the internal master cylinder springs to push everything back. Gene