Submit button remains greyed out - new bug?

Fir the first time in several months, I have just uploaded a large batch of images. I am now going through the process of titling and tagging them for submission. For the first time, I'm finding that for some of my images, always images I submit one at a time, the Submit button never goes green after I have classified, titled, added keyword tags, and clicked No Recognizable People. This is happening to about one image out of every ten.

There is no error message or other indication of what is wrong. Is this happening to anyone else?