I don't know how that was in version 19.1.1 (and prior CC releases) which I installed as first one after many years of using CS6 EXTENDED, and didn't use because of one bug I'm waiting to be fixed, but today just testing something I found another one in 19.1.2.
When once after launching Photoshop I click 'win' key (that is on left side of keyboard between Ctrl and alt keys) then Windows menu (and down bar) shows just for few milliseconds.
Normally that should appear and be present as far as for ex. I won't press 'win' key again.
It behaves so each time I press 'win' key, even restarting Photoshop.
To make sure anything I changed in Photoshop affects this behaviour (like changed preferences, locations of panels etc) I reseted Preferences and Warning Dialogs.
After reopening Photoshop (with default settings) nothing changed.
I found that I may press 'win' key and 'd' what as you should know take me to desktop (or change application by 'alt' and 'tab'). When I then go back to Photoshop and use 'win' key it works correctly! Windows down bar and left menu (the same you can display clicking on Windows icon in down left corner) doesn't disappear after few milliseconds.
I tried it few times more (with just opened Photoshop). Unfortunately each time pressing 'win' key (before eventually I leave Photoshop to be back) makes this bug persists!
I hope you will fix it for 19.1.3 (and check how that was in 19.1.1, and if wrong too then when it was first time introduced).