Display corruption with Lenovo T450 and external monitors
We are experiencing frequent display corruption and flickering when using Lenovo T450 notebooks with the Lenovo Pro-/Ultra-Docks when external monitors are connected.
We first experienced these problems when upgrading Ubuntu 16.04 systems to the HWE stack (with kernel 4.15 and X-server 1.19.6). The systems are using the integrated Intel graphics card (i915 kernel module) and the modesetting Xorg driver. The problems are mostly appearing when the monitors are woken up from standby (e.g. after coming back from lunch break), or when the system was suspended and is resumed. But we also have reports from users, that experience those problems during normal work, but I couldn't verify this myself yet.
Sometimes removing the system from the dock and re-docking it fixes the problem temporarily, but not always.
I will attach videos which show the problem.