Firefox keeps disappearing offscreen when changing orientation.
I am using a Surface Pro 3. Often when changing orientation or coming back after sleeping the computer, a window will whisk away offscreen when I try to click on it and I cannot get it back. It appears in the taskbar (with no preview image), but can't get it back.
You may have a corrupt xulstore.json file. https://support.mozilla.org/en-US/kb/changes-toolbars-and-window-sizes-are-not-saved
Can you open the system menu via Alt+Space?
Start Firefox in Safe Mode to check if one of the extensions (Firefox menu button/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.
- Switch to the DEFAULT theme: Firefox menu button/Tools > Add-ons > Appearance
- Do NOT click the Reset button on the Safe Mode start window