I am trying to create a time-lapse video with photos shot from a tripod every 30 seconds, all with the same settings. When I import the sequence of photos some of them import to fill up the whole screen and some of them randomly import with black bars on the sides, causing a jumpy, zooming in and out effect.

I have tried everything I can think of to fix this. There doesn't seem to be any answers online anywhere that I can find. I want my video to be in the widescreen aspect ratio, but I have tried switching back and forth from this to standard and back, but neither of them works - the photos, even though they are all exactly the same dimensions, taken with the same settings, still vary as to how they are imported. I also tried saving the WMM file to an .MP4 to see if this was just the way the program previewed the images, but the jumpy, zoomy effect still happens in the exported version. I have noticed that if I delete the images that have the black bars and re-import them, sometimes they will come in properly to fill up the screen. However, if I do this, save the WMM file, shut down and come back to work on it later, many of the images change back to randomly having black bars on the side. 

I can post a link to an example .MP4 file if necessary. Thanks in advance for your help with this!