Windows 10: Random instant switch of background after login on slideshow

I collect the nature background pictures from the windows login picture folder rename them as jpg type and add them to a large collection of pictures I use as my backgrounds nature lover here. I have my background set up as a slideshow to switch slides every 10 minutes. During normal use, this 10 minute rotation seems to work on schedule. However, about 70% of the time when I log into Windows for 1-2 years now..., it will rotate through at least 2 slides before stopping., switching every couple of seconds. It is often slides I haven't seen before that only stay on the screen for a se

:)