Hi, I am having the same issue as this person in the AdRotate support forums where scroll bars appear in blocks after upgrading to 188.8.131.52.
However, my blocks are configured correctly. My ads are 300x250 and 300x100 and blocks are configured with the same size. I set both blocks to have 0px margin, padding, and borders.
I downgraded to 3.8.3 first to fix the issue.