It happened to me this after the update to windows creators last week.
It seems to be the Mix between OneDrive and Wamp, maybe something about the Onedrive lock the files to other processs.
I have the same situation, I have tested wamp 3.06 thru 3.1 and the result its the same.
I've changed to another directory out of one drive, and it works well.
There will be some work on this line
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