DAF ENGINE WARNING

Basheer:
I have some issues with brakes for my DAF CF75 Year 20017. At times the brakes are ok and at other times no brakes for some time. I had the braking mechanism checked (all brake disks and rings etc). No fault on the dash board. Yet the problem persist. I had the rear modulator changed, the front modulator changed, the four circuit valved changed on the Air dryer and the redundancy valve changed. The problem still persist, i.e at times good braking and at other times no brake. Can anyone advise. Thanks

Footvalve?
Brake pedal free of crap?
Small pipes near the footvalve kinked?