Hello,
I have a Surface Book 2 (3000 x 2000 at 150% scale) and an external monitor (3840 x 2160 at 100% scale). I use the external monitor as my primary monitor, so I usually keep most of my text editing there.
When I close Sublime on the secondary monitor and then start it up again, the position of Sublime will shift diagonally up and to the right by a bit. So eventually, it will start off-screen, and I have to use Win + Arrow keys to get it back.
Closing it on the primary monitor works correctly.
I think that the startup position is not handling different DPI scaling on multiple monitors correctly.
If I set both monitors to the same scaling, it works correctly.
The direction of the travel of the startup location is also dependent on where the monitors are arranged in display properties. So if the secondary monitor is directly above the primary one, sublime will simply move straight up. I have it above and slightly to the right, so it explains the diagonal travel for me.
Sublime 3.2.1, Build 3207
Windows 10, Version 1903