VS Pro 2019 Sudden change in video size

[mytq1354]

Have been editing a project for weeks and was in the final stages when the size (i.e., aspect ratio) suddenly reduced. I cannot find a way to get it back to the original size. It also switched from 4:3 aspect ratio to 16:9. Any ideas on how to fix this would be very appreciated.

[jorgensen]

Project settings are in Settings->Project Properties
The format settings can be a little tricky, but not impossible.