As far as I can tell, I’m running the latest Tobii software, at least I get no updates when I check for them. I posted the precise versions above.
It doesn’t seem to matter what window I’ve focused, I’ve reproduced this in Firefox, Notepad, the Windows start menu, Windows settings, Tobii settings, Explorer, etc.
A low level keyboard hook (WH_KEYBOARD_LL) shows me injected keyboard events (flags: LLKHF_INJECTED, vkCode: 37, scanCode: 0; as opposed to regular inputs that have a scanCode set), most likely sent by Tobii software.
As for when exactly it happens, refer to the following screencast – it also seems to depend on what’s in the background: http://download.tiitoo.com/screencasts/2017-11-15%2017-09-20.mp4
In case it doesn’t reproduce for you, did you try this on a Windows Insider Build?