The administrators have moved Moodle from a previous (I guess 3.6) to 3.9 version. As a result I found all my small web sites that were included in the course (using file resource and setting index.html as main file) with problems.
They show now with a fix height size of near 550 pixels. Too little, since many of these html pages include flipbooks (png images) that now cannot be read, since they are rescaled in height instead that in width as it was in previous Moodle versions.
The vertical constraint of the frame is the problem.
The image below gives an example. Can someone help to suggest where to look at the issue (in the admin side I guess) so to remove such a constraint?