I wanted to provide you with an image example. So, I went to POF and I found a random female profile. I right-clicked one of her pictures and selected "open image in new tab". This was the resulting URL link.
https://pics.pof.com/dating/1180/3/51/5149aea79-8bee-4825-9ee9-3c6cdb432244.jpg
I then tried doing two things.
1.) I tried zooming in to 400%. Then I used the page's horizontal and vertical scrollbars to see other parts of the picture. On the left side of the image, it was missing a lot of her head. I could only see maybe half of her forehead. On the top side of the image, there was a lot of image missing to the right of her face.
2.) I then did a full reset and rotated the image 90% to the right. I then zoomed in to 400%. I used the page's horizontal and vertical scrollbars to see other parts of the picture. On the left side of the image, there was a lot of image missing to the left of her face. On the top side of the image, it was missing most of her head. I could only see the bottom 25% of her eyes and nothing above her eyes like her forehead or hair.
You may get slightly different results using the above steps, as it might be dependent on how big your browser is and what your desktop resolution is. I am using a 1600x900 desktop screen resolution (you can change desktop screen resolutions in Display Settings). And the browser window was sized to around 1050x870. The truth is, even if I made my browser a little bigger like 1600x870 (taskbar covers up the bottom 30px), I would still have the same problem. Like in second example, everything above her eyes would still be cropped out. If you tried to replicate this issue, I would suggest maybe temporarily changing your desktop resolution to 1600x900 just in case. And if you get slightly different results, maybe try using a larger zoom like 500% - 900%. But this problem definitely does exist. It's been bothering me so long that I just never used the feature. In fact, I was just now looking online for another Firefox extension that could replace yours. But I only found one where it just rotates the image 90% to the right each time that you use it. It did not have flip and zoom features. So I thought maybe if I could get you to fix your extension, I could just stick with yours. I have seen in a previous post where this was blamed on child page elements and stuff like that. But the URL I provided you with is goes directly to an image with no other page elements. I may be wrong, but I think that this bug affects rectangle shaped images and not square shaped images. It probably affects all image shapes though. I just looked on the closed issue dates and this was reported almost 13 months ago. I can't believe no one has reopened this issue or that the issue hasn't been worked on or fixed in those 13 months. Let's try this again. (fingers crossed)