I have the maximum image size upload set to 10MB as you can see in the screenshot below.
I attached the 4 images that someone is trying to upload. I tested them and then my hosting provider liquid web.com tested them and we all get the same results. Here is the info from the hosting provider:
After doing some testing, I suspect there may be a per-file upload limit being imposed somewhere that isn't listed. I noticed that images 1 and 3 which upload are over 2MB, while 2 and 4 which don't upload are over 2MB. I tested uploading some other images and found the same pattern that images over 2MB wouldn't upload. I found that the PHP upload_max_filesize was set to 2MB and increased that to 10MB, but am still seeing the same behavior when trying to upload images over 2MB.