We have, as recommended, enabled the Redirect to the canonical URL to 301 redirects, however social media share buttons on product pages now won't work properly. Having used Facebooks testing tool, the error is "URL requested a HTTP redirect, but it could not be followed", turning off canonical URL makes it work OK again. We have attributes on most of our listings therefore we would obviously rather not have duplicate content, and therefore would prefer to keep the 301 redirect, but it literally breaks social media sharing on Facebook.
PS 1.7.6.5 but was present also in 1.7.6.4