All updates 
By Denny Beats, Product Owner
Web Release 226.0
Fixed Instagram post previews so they accurately reflect the final result after automatic format adjustment (fit/crop), including the cover.
By Denny Beats, Product Owner 
Update
Instagram — correct preview after automatic format adjustment
Fixed an issue where, after enabling automatic format adjustment (fit with borders or crop), the post preview could show the video in its original look even though the final published file was correct.
Now the preview always matches how the post will appear when published, including the selected cover.