I am going to put this out to see what if any ideas you all may have. My 2015 Base has had brake pedal fade since it was a pup! But it is an interesting condition that as of today no one can put a finger on.
In an attempt to fix the issue here is what we have done.
1- Added a big brake kit hoping it would solve the problem - just magnified the issue
2- Multiple digital wrench ABS brake bleeds
3- Fluid Change
4- Manual activation of ABS on gravel road.
5- Checked the master, you can hold pressure on the pedal and it holds firm.
The condition is extremely perplexing because at or around sea level the brakes perform consistently pretty well. Occasionally after a long run without using the brakes you may get a slight pedal drop at first application, quick pump and you have full pedal.
This is where it gets weird - In the mountains at most any altitude with lots of hills the pedal will drop to the floor inconsistently. Come back down out of the mountains and the pedal comes back to normal.
My guess is there is still air somewhere in the system most likely the ABS block. Thinking possibly the change in altitude is allowing the air to escape due to a difference in pressure.
Would love to hear any other opinions!