I went made a copy of your latest email, and inserted several of your most recently added images to the copy. I'm afraid I didn't come across any that showed as inverted when inserted. If you have a specific example of a pic that isn't in your Library, please reply directly to the automated @ mentioned email you receive from my response, or call our general support so we can directly collect it and troubleshoot further.
If the example is an actual thumbnail being provided by inserting a YouTube or Vimeo link into a video block, please provide the URL you're attempting to insert, and an example of what the image should look like, in your reply email / call-in.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ William A Community & Social Media Support