I have created a HTML file in developer workbench with three reports in it, all Active reports, aligned in a horizontal line.
If I select the Active Report arrow for the report on the far right, the Active report window appears over the report on the left. I have attached a screenshot of what happens. I have circled the Active Report arrow I selected and you can see where the window appears.
I have been creating these HTML files for quite a while. We have recently migrated to v2.1, which is when this issue appeared.