I've also had the same problem - Upgrade Mac 2015 to 2017 and bought a USB-C dock for two external monitors.
Before installing Displaylink, my StarTech dock only supports on HDMI monitor, but iTunes content works no problem. Once I've installed Displaylink 10.14 both monitors are supported, but I cannot play iTunes contact on ANY screen - The two external monitors or the Macbook Pro's own screen.
Tried SD content instead of HD - Same issue, but with SD content I can heard the audio, but there is no picture.
Both Monitors support HDCP, the Macbook AND the hardware of the dock, so the issue (as noted on other feedback) is DisplayLink drivers.
JohNB
I've also had the same problem - Upgrade Mac 2015 to 2017 and bought a USB-C dock for two external monitors.
Before installing Displaylink, my StarTech dock only supports on HDMI monitor, but iTunes content works no problem. Once I've installed Displaylink 10.14 both monitors are supported, but I cannot play iTunes contact on ANY screen - The two external monitors or the Macbook Pro's own screen.
Tried SD content instead of HD - Same issue, but with SD content I can heard the audio, but there is no picture.
Both Monitors support HDCP, the Macbook AND the hardware of the dock, so the issue (as noted on other feedback) is DisplayLink drivers.
Please can you look into this ASAP!!?