Using PE 13, with 4K video, and a photo as the media (also a separate audio track).
I have never seen this happen:
1) Before rendering, the preview looks normal...the video is correct...
2) after rendering, the video (but not the still image) is massively cropped (about 50%).
I am mixing a photo into the project (which I have never done before if memory serves), so is there something about the photo's presence that is affecting the rendering?
I created a new project twice...once by inserting the photo first to the timeline (I read that PE sets the "project properties" by the first media dropped onto the timeline? If that even makes a difference in the final output?), and a second time by dropping the video in first.
After each rendering, for some reason, the video is cropped/zoomed to about 50% of normal size...the still picture looks normal...so it's only the video that is being affected.