@seconsmkrc Hmm that's interesting, I thought I'd try it not expecting anything out of the ordinary but this is my result, 🤔 Hopefully it will be something simple....

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The file I used above came directly from my Samsung S23 Ultra phone, I rendered it with Vegas (no mask, just the file) & got the correct result this time, I suggest you recode your file with Handbrake etc. or render it out using Vegas. (I think someone also suggested nesting the orig file as an option.)

It must be an issue with certain file types, this is MediaInfo of my orig file. maybe the Rotation.

This is a link to a similar problem & quoted from the link by @john_dennis As cool as it is to just throw a bunch of files onto the timeline and edit away, sometimes it's more sensible to prepare your media ahead of time.