Dual screen wallpaper, and somehow wallpaper reverting back to Galaxy

[Sevenstring]

For years my preferred wallpaper has been the Aqua blue / Galaxy wallpaper for both of my 27 inch 2560 x 1440 screens. The other day, I happened upon a site that has some dual screen wallpapers, and one of them looked cool on my computer. I changed both screens and the picture spans both screens...look cool. I worked with it for the day, and I dug the look. I rebooted and the wallpaper reverted to the galaxy paper. HHmm? I re-did it and the same happened. So this time I decided to do a search on the subject....I am not alone. (Photo # 2 is the stitched images together as one)

I found a lot of suggestions including one that comes close to resolving the issue, but as they say...close is only good in Horseshoes!

Someone suggested that in Preference we click on "Mission Control" and remove the check mark on "Displays have separate spaces" This effort sort of worked except on the left screen we lost the Menu Bar, and after the first reboot only the left screen was the Hawaii picture, the right screen returned to the Galaxy....I had to repeat the process, and finally the left and right screen returned, but they were reversed....all ready, I was thinking that this is a bigger pain in the .....than having the galaxy wallpaper...I finally got both screens working, but again the menu bar is missing on the left screen....(unacceptable)
p.s. the files are in the correct location. Any thoughts or suggestions? Thanks

 

[MHenr]

I have the same issue. My setup is a 13" MBP (used in clamshell when I'm in my office) with 2 identical monitors connected through USB-C/DP.
There is no solution for this afaik, and it's a known issue.

If you're having trouble with screen arrangement as well (I do), this could help;
This command line utility, but I've never used it.
It is used to configure multi-display resolutions and arrangements which can be programmed to a key combo.
So every time you wake up your computer and the arrangement is wrong, a simple key combo can be used to set the correct arrangement.

 

[Sevenstring]

MHenr. Thanks for your response....I was beginning to think that I was alone! loll...Sadly since then my cMP died, and I was forced to replace it with a newer unit. I was extremely lucky to find a 2012 dual CPU unit at even less than the price I paid for the first unit. For some reason (I cannot explain) the wallpaper now works in this newer unit....here is a relevant fact.....when I received this new unit I removed the already installed drive caddy and replaced it with my unit. (A 500GB SSD with all of my programs and Mojave installed) One of the best aspects of the cMP is that all the hard drives are easily removable. It booted up normally and I tested the wallpaper...dig this! it works now....Knock me over with a feather...I cannot explain, or even suggest an idea of what has changed. (It is not the video card because I put in my video card). I basically gutted my old cMP and fitted the new one with the old parts (memory and hard drives) Go figure...I cannot explain, but as you suggest it is a known issue. I know this does not help, but good luck to you and thanks for your input. RC