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Did you find a solution? Because I've had this happening to me, too. 

The only somewhat solution I've found is to copy the frame you need, then paste it behind the first frame (so it becomes the first frame)

Exit the project then reopen it

Put in the image you need

Copy the frame

Then paste it back where you need to be. 

It's a lengthy process, but it's the only solution right now that I can find, because others are having this problem too. 

I've been having this problem too, did you ever find a solution?