I have fitted new front pads and rear slave cylinders (drums on the rear).

I had to force the front pistons back to fit the new pads.

Now I have a soft pedal, long travel before the brakes start to work.

Pump the pedal and feels OK till next time.

Hold foot on pedal and it slowly goes to the floor.

We have bled the brakes twice including the proportion valve.

Any ideas what is playing up.