DisplayLink are only the Video, audio and Ethernet part of the dock. The USB hubs in the dock (which would connect your USB keyboard would connect through) are not from DisplayLink.
I'd check if there is an update to the USB hub in your dock (you don't say which dock you have) which would be available from the OEMs website. I'd also see if it happened on USB 2.0 aswell as USB 3.0.
Wim
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