This problem is really easy to understand and replicate, but I haven't found anyone else with this problem, at least according to google.

1) I open a photo, any photo (Microsoft Photos 2018.18091.17210.0)

2) Zoom in, using any method

3) Do a single click somewhere in the Photos window

4) The image, after the top toolbar drops down, zooms out to show the whole photo.

I just noticed that when you click in photos, at any point, the top bar slides away or comes back down with each click. For some reason, this toolbar coming down auto-unzooms the photo. This may be related to the fact that if you adjust the Photos window size in any way, the photo also unzooms. That top toolbar appearing reduces the available screen real-estate and so, just like adjusting the window size, the image unzooms. Pinning the toolbar would solve this, if my theory is correct, but that doesn;'t seem to be an option.

Also, I have tried a couple other photo viewers, but all were missing some critically obvious/simple feature that I'd rather have and deal with unzooms, than not have.

Thanks for any help.