Thanks for your feedback.
1 - I have had the robots.txt file live for a couple of months. I tried the tester and it says it is working fine. But Google still seems to be ignoring the
Googlebot-Image - Disallow: /
command and it is still continuing to index more and more images from our site on an ongoing basis. That is why I posted the issue.
2 - The Bot No Access permission setting is a standard setting under forum permissions. Normally it is used if you have private forums that you don't want indexed by search engines. We have about 5 of these No Access forums already in place that we had set up on the site since the very beginning. And we never got any warnings from Google that the forums can't be crawled. So it was never a problem before and they just ignored them. Then we recently added a new private forum which we also don't want crawled and suddenly Google is flagging that as an error. Normally Google understands the No Access setting and never raised an issue with it. But as you said, I can just ignore the warning in the Google Search Console about it, but it is confusing why this would be triggering a warning in the first place when it is something Google seems to understand and it has never caused an issue in the past.
The only thing I can think of is we are running an extension called "phpBB3 SEO Sitemap" (https://www.phpbb.com/customise/db/exte ... o_sitemap/
) which creates dynamic sitemaps. Perhaps this extension has included this new "don't crawl" forum in the sitemap when it shouldn't be and this is causing confusion with the Google bot and triggering the error? I don't know, its just a guess.