Brake pedal intermittently sinks to the floor no fluid leak master cylinder in new what could be causing this?

What is your question?

Brake pedal sinks to the floor randomly. There are no fluid leaks and we changed the master cylinder and bled the brake system twice and the brake pedal still randomly sinks to the floor.

What makes this problem better or worse?

Nothing has made it better or worse

How long has your 2009 Scion tC had this problem?

Couple months