Yesterday Lenovo released a new firmware for the USB -C Hybrid dock, wich can be found here:
https://pcsupport.lenovo.com/us/en/downloads/DS504448
The changelog sounds promising as I have connected the external Displays via a DP to DVI Adapter:
Cypress FW:
[V0.2.68] 2019/11/13
1. Fixed external monitor attached on dock no display or light up slowly if connected through DP to DVI dongle(lenovo PN43N9159).
2. Optimize LED breathe more smoothly.
Billboard:
[BB R38] 2020/01/13
1. Fixed external monitor attached on dock no display or light up slowly if connected through DP to DVI dongle(lenovo PN43N9159).
VIA HUB :
[Hub1 5543, Hub2 5544 ] 2020/1/3
1. Fixed external monitor attached on dock no display or light up slowly if connected through DP to DVI dongle(lenovo PN43N9159).
2. Fixed USB2 doesn’t functional intermittently when work with ThinkPad X280.
3. Fixed USB hub FW update failure while full loading when work with ThinkPad T480.