Yesterday I solved the problem.
First I uninstalled the Intel adapter in Device Manager using the option to also delete the drivers.
Then I went into registry and found 2 different entries for the adapter under:
There are different registry key branches each representing the network adapters. I removed everything Intel (VEN_8086) by deleting the appropriate key branches.
After a reboot I reinstalled driver software 17.1 including the additional device manager tabs from Intel ProSet.
I de-activated power saving in standby and enabled WOL from standby and WOL from power off.
After that the following happened: when shutting down the PC the green link LED on the switch representing 1000 MBit/s went off for a short period and then came back in orange (100 Mbit/s). Now the PC is ready for WOL again!