The TL;DR summary: In February 2017, when Elsevier were accused of selling one paid-for hybrid open access article, at first they sowed doubt about it, then three days later admitted it to be true. In their admission they state that it is the only wrongly paywalled open access article “affected” at their websites. They have apparently checked their “system” and say there are no more wrongly paywalled articles at Elsevier websites. Their statement is however demonstrably incorrect as I show in this post. There are more paywalled open access articles at Elsevier, and by their own admission Elsevier don’t seem to know about them. This is professional incompetence. HybridOA as whole, not just at Elsevier, is not reliable. We should not use hybridOA services if we actually want reliable open access in perpetuity.
According to data Wellcome Trust has made available, in 2012 they paid Elsevier £5,280.00 to make the article in the screenshot below, open access in perpetuity. In 2017 I find it is on sale at ScienceDirect for $35.95 + VAT. I bought access to it just to verify that it is actually on sale and indeed it is.