EZ Page - Some Video Only Play Audio

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I have a curious problem with some, but not all videos I have linked on an EZPage. All videos (MP4) play correctly with video and audio, locally on my PC, so I know the mp4's are good. I've uploaded them to my server, and link to them in an EZPage. Some of them play correctly with video and audio. But most of them play only the audio.

I'm not using any embedding code. I simply place a still png from the video on the page. Then I click the image and select "Link Image" button to link a video to the still.

Here's the page where you can see what's happening. https://australianbakerycafe.com/reviews-media-ezp-39.html

Ignore the Bluegrass Jam image (which is a YouTube search link)

The first video of Susan Parker plays normally. The second, Hot Cross Buns -- sound track only. All videos load, but some of them are audio only. Any idea what's going on here?

Thanks.

Your videos are not compatible to standards.
If you like send me your mail address and I will send you one edited clip via my Cloud Storage.

Thanks Shop Suey, I took the ones that wouldn't play and "converted" them to .mp4 (they're already mp4) as a _new.mp4, and uploaded and linked. They play fine now. Thanks for the tip. BTW, I used VLC to convert, or, re-recorded them.