thanks for the answer
did a system restore and got back the Intel iris 6100 driver v10.18.15.4248 (was on v10.18.15.4256)
and this solved the problem , all screens are again working
now at the same time it rolled backup Windows update KB3081448
will see what happens when that one reinstalls itself...
but first impression is that the latest driver caused the lock out of the displaylink device/driver
Thanks for the information. I am glad the system worked by rolling back to a previous driver.
that was for a short period, after a break and the monitors went to sleep
again only possible to get only two of three monitors working
so what I did was (in the meantime KB3081448 Win10 update was installed on the background)
removed the Iris & display link drivers
started up without any display drivers
after a couple of minutes (was busy unzipping Intel Iris 6100 driver v10.18.15.4248) he monitors flickered
and Windows 10 self installed Intel Iris 6100 driver v10.18.15.4256
and then it asked to install the display driver
all automatically without initiating an install , probably related to following setting
but never saw this really working in Windows 7....
so disabled it to freeze the actual config
I understand, let's hope future graphics drivers for Windows 10 addresses any issues with the graphics controller.