This issue has been closed as 'Won't Fix' due to an extended period of time without updates. If this issue is important to you please let us know by posting on the AnswerHub or UDN, and Epic will re-open the ticket for further review.
A packaged game that is ran with -fullscreen shifts position when entered windowed mode.
I am not seeing this issue when running an unpackaged project with -game -fullscreen.
I am also not seeing this issue when starting the packaged game without -fullscreen then spamming alt + enter.
REGRESSION: No, this issue also occurs at 2386770
Edit MattK: This has probably nothing to do with the content and is most likely reproducible on a blank project
1. Copy the LandscapeMountains folder from the network to your computer (see comments)
2. Navigate to the LandscapeMountains folder
3. Run the packaged executable with -fullscreen
4. Press Alt + Enter several times
RESULT:
The location of the game in windowed mode shifts when switching back and forth between fullscreen and windowed.
Head over to the existing Questions & Answers thread and let us know what's up.