Brake pedal slowly sinks to floor

My turn to chime in. I have 2- 2018 tacomas (yes twins) and both of them will do the same thing with the pedal. In fact just today they replaced the master on one of them cuz of s recall. That trucks brake pedal still will slowly sink to the floor. Both trucks have done this since new. You tell me?
I can pump the brake really fast and it stiffens up but if I hold the pedal hard, it slowly sinks down.

 

We have a 2013 - never had an issue with the brake pedal falling, was always tight. My dad changed the front brakes on it today, now it’s no longer tight. The pedal falls after you come to a stop and when you are sitting still, you can push it all the way to the floor. He says it’s a master cylinder because he never touched any of the lines. I’d prefer not to get work done that doesn’t need to be - any suggestions appreciated. Thanks!

 

Turned out to be a recall and they replaced the master cylinder

 

Although rare its possible the new one is bad. Which it turned out to be Brakes are supposed to hold position, you shouldnt have to pump them and they shouldnt "bleed" down. IF they do then theres a problem. Push brakes vehicle slows down pedal stays at proper position, doesnt bleed down thats how all brakes should work.