Welcome to the forum Simon.
I found looking at the photo "in a new window" gave a closer image. I 'm not very good at making things out in reflections, so maybe others can comment.
Can I ask if you have had activity at this property and if so- what? Also how long you have been there or has it been going on?
I have been an investigator for a time as well as had plenty of my own experiences., so would put images caught in windows along with other events rather than treat them in isolation. There is of course the possibility of natural reflections.