Add a [/embed] tag at the end of your videos (so for example the BBCode of your first video will turn into [embed=https://www.youtube.com/watch?v=JAcksLA1GXE&feature=youtu.be][/embed]). This shouldn't normally be necessary, but I've noticed that the issue you describe can be fixed by it. In the meantime, I'll do some research on why this happens in the first place and ask the developers to fix it once I find out.
Thanks to jhoijhoi for the signature!
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