Good morning everybody. Slept like a log.
This is what I do:
#1 - Check my Project Properties: Have I set/corrected for 16:9? Go File>Properties>Template
#2 - Check my Event Properties: Right click on an Event, open "Properties" and click on "Media" tab and confirm my "Pixel Aspect Ratio" (PAR) is correctly set to my media.
#3 - Check Aspect Previewing: Right click on the actual Preview Window and confirm "Simulate Device Aspect Ratio" is checked.
. .and that's what I do.
If THIS doesn't sort you out then get back here.
Grazie