Windows 10: Lockscreen wallpaper changes automatically

I use windows 10 home. I have my lockscreen wallpaper set to picture mode and i have no clue how this keeps changing to some other random picture which i never had on my device before. it keeps happening with two pictures only, i have not seen it change to any other than these two .

This is so frustrating. Help please!

:)

 

Lockscreen Wallpaper

I am unable to change the lock-screen wallpaper. Whenever I select a picture to set as lockscreen, a message pops up saying"try a different photo". If I try to change it from the personalize window, the picture keeps buffering and there is no actual change.

 

Wallpaper and lockscreen images are automatically changed

Problems is as described: I set my wallpaper to an image of my preference and when the computer is connected to the internet, the wallpaper changes to a different landscape picture after a while, without my consent or desire for it to do so.

Facts, before someone asks:

• I don't have Bing background installed or whatever it is called, at least not that I know (I searched)
• Wallpaper is not set to do a slideshow and the images that show up are not mine
• I haven't personally installed any software that would do any of this
• Computer is protected by a security suite (ESET Smart Security, updated and up to date) and is clean

I'm a relatively tech-savvy person and I'm only here because I haven't been able to solve this, not even by googling, not even going to other forums, nothing. I don't know where this comes from, I've investigated all other possibilities and I still don't
know what is causing my background to change. My last suspicion is that Windows downloaded something or brought something in an update that is doing this.

Oh, and I have a W10 laptop (x64) and the problem doesn't happen there.

 

Bing Lockscreen Wallpaper does not update

My Bing Lockscreen Wallpaper is working now, but with a little bit different compare to bing search background

- my bing search background changes from 4PM everyday

- my bing lockscreen wallpaper changes from the next morning, maybe in the previous night because when I wake up (6AM), it's changed.

I'm in Vietnam (UTC +7)