I am also experiencing this issue after a recent backup, very frustrating to deal with especially while trying to rework a villager farming setup. Hopefully support can resolve this soon!
I am having the same issue after reloading a backup save after a crash, it seems that there is something causing the settings to default after a reload.
Hi RMZ, I just tried out what you recommended and it worked! Thanks so much for the pointer, it was as simple as temporarily toggling cheats in the world menu to edit the lock time setting back to normal and then reuploading the world after confirming that achievements were still enabled. I’ll try to spread the word on this issue as it seems to be impacting many people who have realms with large file sizes! Thanks again and Happy New Year!