Window mapping errors in Cb Pro 8.5 on large display system

I have a Windows 10 system with two displays; the main one is 5120x2880, the second one is 2560x1440. They are mapped as an extended display, which is great because I have lots of pixels for lots of tracks and mixer channels.

The BUG is that intermittently Cubase Pro seems to lose track of where the window boundaries are. The main window header (with File, Edit, Project etc menus) can be moved to either the 5k or 2.5k display. If it’s on the 5k display, then sometime the mouse cannot select the right menu items because the pointer is painted in a different place to the selected menu element. But if it’s on the 2.5k display, then sometimes clicking on ANY menu in the header does nothing, and the only way to restore responsiveness is to move it to the 5k display and back again, sometimes multiple times.

The transport panel popup window seems particularly problematic. Often just dragging it around on the 5k display leads to the entire window “jumping away” from the mouse and continuing to move further up and to the left. It looks suspiciously like some cache programmer did not expect pixel locations ever to be greater than 3k, and so the transport window is constantly reassigned to a position “modulo 3k”…

Needless to say this is extremely irritating and I was wondering if anyone else has similar experiences with large multi-display systems on Windows 10/Cubase Pro 8.5?? I could not find anything in the existing bug list, but maybe I’m not searching for the right terms…