Ronald —
I had a thought, and am going to make a speculation, that might not mean anything — but maybe the error message was manifested by some interaction with the server setup —
I am wondering this, since the original 9 sites where I ran into the issue and then deleted it (sorry I should have made a screen shot before doing that) —
but all those sites were on SiteGround.
I just took a look at a similar site that is hosted on CloudAccess — and that WP install basically has a similar set of plugins, theme, etc — but interestingly it did not have that error message.
That got me to thinking that given the other sites had all been hosted on SiteGround, perhaps there is a server interaction that is creating that error message.
I do know that SiteGround has this entire proactive deal that goes on where seem to like to make it difficult for anything to block their push to auto-update their users. (I had run into this issue a few versions back when SiteGround completely over-rode my settings on Easy Updates Manager and auto updated, with no regard to my settings. But this weirdness seemed to stop after that one time a few versions back of Easy Updates Manager.)
It would be interesting if you might be able to get a read from your other users who have also seen that error message and find out where they are hosting, and see if there is something connection to where the sites are hosted and where the error message is showing up.
Just a thought — (I know there have been some other recent plugins recently where something, some setting SiteGround had that caused/made the plugin have a bit of weirdness happen, until the plugin developer made some sort of tweak.)
Thank you in advance.