[2023] Cursor loses focus on dual monitor

Re: [Mouse Drifting off Screen](/topic/83416/mouse-drifting-off-screen)

I have a similar, if not the same, issue with AC Valhalla as the above post describes.
I have only recently started playing this game and have this issue that I haven't had with any of the other AC games.

I have a dual UHD monitor system with each screen driven off a different GPU.
The games are played on the primary monitor.
With Valhalla, the mouse cursor will often slide over to the secondary monitor when I move the mouse to the right and I lose focus from the game.
I have to move the cursor left again, back to the primary monitor and click on it to move focus back to the game.
This usually happens when in combat so it can be very dangerous for Eivor.
Does anyone else have this issue?
Is it a bug?
Is there a fix or workaround?

Thanks for any help.

Tech details:
Windows 10 pro running on Intel i7-6700K @ 4.00GHz
32GB RAM
Primary GPU NVIDIA GeForce GTX 970 with 1GB RAM
Secondary GPU Intel HD Graphics 530 with 1GB RAM
Games are running under Steam in full-screen mode.