U2414H, daisy chain problems

A good customer of us bought 6 x Dell U2414H monitors. 4 x for her laptop and 2 x for her assistant's laptop. Bought lapstops are the HP ZBook 17 G2 Mobile Workstation (J9A21EA#UUG) with the A7E38AA Advanced docking stations. The Dell screen are connected with the laptop through Delock 82770 Premium Displayport 1.2 cables. Both laptop and docking station have Display port 1.2 connectors and is capable of using 5 screens on 1 device (internal laptop screen + 4 external ones).When connecting the Dell screens with al the video connectors on the laptop and docking stations, the screens are working perfectly. When trying to use the Dell U2414H screens in daisy chain with all screens set to displayport 1.2 in the screen menu except the last screen, sometimes this setup is working but most of the time, the screens in the daisy chain stays black when the laptop is powered on or the laptop went into sleep modus. And this problem is on bought laptops with 4 and 2 Dell U2414H screens. Tried different videocard drivers, displayport cables, the displayport connector from the laptop itself and the docking station. Also tried the change the order of monitors in the daisy chain. Any idea what the problem is or the solution?

Bye,
Dimitri Snijders