This may not be helpful to you, but I had something vaguely similar some time ago and it might be worth considering in any case.
I had a problem with the classic photo viewer in W10 (re-enabled via registry). Out of nowhere suddenly had these weird hangs for several seconds before the photo viewer would open to show even small double digit KB jpegs. It did all the time. I wasn't until I used Microsoft's ProcMon program in a last ditch attempt and, to my surprise, found that there seemed to be a lot of Nvidia driver-related activity that seemed to start, halt, then carry on again that coincided with when the jpeg was double-clicked to open, going through to when the photo viewer finally stopped hanging and displayed the image a few seconds later. The notion that I could have graphics sw/driver issue baffled me, because I would have been certain I'd see issues elsewhere (games, media player classic + madvr, chrome's gpu acceleration). However, perhaps there was just an issue with the sequence of events the photo viewer was taking to render out an image (for example, old photo viewer seems to rely on d3d9, as well as icc color profile), or an issue along the way not directly related to the photo viewer but also not affecting other programs too. I did fresh install of the Nvidia drivers and the issues completely went away. That was all it needed. Maybe it wasn't a graphics driver issue, but something elsewhere in the OS that a driver reinstall helped - I don't know. It worked though.
Since then I've abandoned both the old and new MS photo viewers and gone for Irfanview instead, though there are plenty of other 3rd party options too.
tl;dr - Try reinstalling graphics drivers
