In the end, I gave up using WordPress plugins. Now I am using IFTTT applets to generate tweet with images from the RSS feed of the site. It works and this is what matters to me.
By the way, the problem was not the publishing of thumbnail images.
My issue was related to published tweet with thumbnail images linked to “ghost” articles that weren’t stored anywhere on wordpress. The only possible source for the inormation used in those tweets were the contents pulled by Cybersyn…
