I've set KLWP to both homescreen and lockscreen, but when I do, changes are not implemented when I tap save. This issue is not present if KLWP is on the homescreen only.
The only way (that I've found) to update changes when KLWP is on both screens is to restart my phone, or to change the wallpapers to something that is not KLWP, and then change back to KLWP.
This was not an issue for me in the past (maybe a year ago?) when I was creating a different theme. I am using a Samsung Galaxy S7, Android 8.0 and KLWP Pro (updated to most recent version)
I've already tried deleting cache for my launcher, cache for KLWP and have reinstalled KLWP. Issue persists.
I also found an old thread that looks to be discussing a similar (or the same) issue. (Here)