Pressing X on full screen image jumps back to top of article

Hello all. I just noticed a bug on my website which seems (I never actually noticed if this happened before or not) to only be since I did the latest 4.3.1 update on WordPress.

This occurs when I click on an image that is part of a gallery, to open it in theatre mode. Whenever I either press the X to close it out or click anywhere back on the article to close it out, my article will jump back to the top.
I noticed that a # will also be added to the address link when this happens.

For example, trying with this article: https://www.abridgedpause.com/boize
After X-ing out of an image, you will notice that the link will then be https://www.abridgedpause.com/boize#

I find this jumping back to top issue incredibly annoying since my articles are usually very long, and I have no idea what could be causing it. Could anyone please suggest something to help me fix this.

Thanks in advance