I have a Toshiba Portege z20t upgraded to Windows 10 and connected to Toshiba Dynadock 4k. I also had the two screen flickering/switching problem that made them unusable and this seems to have stopped the z20t from recognising its keyboard dock. However, applying Bob's fix at
http://plugable.com/2016/01/19/flash...-7-9-m4-driver has enabled me to get Dynadock 4k unit working again via micro-USB socket on z20t tablet.
I still do not know how to get tablet to recognise its keyboard dock again