I received newsletter from CrossRef and among several things I found out that they will change redirect method:
We have decided to change the HTTP redirect code used by our DOIs from 303, back to the more commonly used 302.
Please advise how this will affect users of OJS.
I do not think it will change anything. The DOI will still look the same and from the user point of view it will work just like before. Just the redirect code in the header is different, but the result is the same. See Redirecting redirection - Crossref
“Note that these changes will not affect users or machines using DOIs. The change should be entirely transparent.”