Hiiiii I've had the same issue for the last few weeks, I'm playing on console (ps4 pro specifically), I am able to upload sims to the gallery but not lots, I have tried multiple lot sizes on different saves, before I had even interacted with any burglars, no burglar alarms in any saves, lot saves won't upload to my gallery giving the same error message as the post says up top.
here is a lightly edited video for specification https://youtu.be/bbgT9IOV2SI?si=JmlUFtRNSyNs1Pri (unlisted)
here is the unedited version https://youtu.be/bHcXawtUiTU?si=peZyuCx09GJugyI4 (unlisted)
hope this helps and good luck solving it!!! happy to clarify anything
(for what it's worth, around a week ago I was editing a build and every 10 or so minutes I'd get completely kicked from the game to my home screen with an error message, saying something like it crashed, don't know if that has anything to do with this bug though - although when that was happening I was able to save individual rooms, but not the full lot because of the gallery error thing)
EDIT: 40 minutes later, the lot had been added to my gallery despite the error somehow, still gives me an error and doesn't say that it's been added to gallery but I can at least add lots to my gallery now!!
2nd EDIT: 10 minutes later - Okay it's actually totally fine now, no error, saves like normal - I didn't do anything, it just fixed itself it seems yayy : )