Being someone that is passionate about Forge, it’s been a very bittersweet experience for me. I’m won’t beat around the bush but here are some issues and some suggestions for fixes that I have been experiencing and would like in the near future.
Desync - yeah it’s a bummer, it’s a game wide issue effecting anything that is online. It specifically affects object placement, object editing and even loading in prefabs. Prefabs will load in all… uh… wonky? Not the way they were saved is the best way to get the idea across.
Connection issues - This probably goes hand in hand with Desync but this can occur relatively often. Error message will be that you have “Lost connection to game servers” resulting in any unsaved progress to be lost, and thus reverted back to last save. (However I am now aware that there should be a auto save if a session is ended abnormally, but doesn’t happen due to a bug)
Crashes - On Xbox series S here and this mostly happens during object scaling. Sometimes objects such as UNSC Floor fails to scale (nothing happens when said axis is edited) and after a few moments the game will crash. This can also occur with similar objects when changing object textures.
UI - Some options in object textures tab are blank.
Potential fixes for said issues, notably connectivity issues.
Local file saving - Forging offline is actually possible by going into Custom Games Lobby and changing the server from “Xbox Live” to “Local” and then going back to the forge menus and loading into a session, however the kicker is that players are unable to save due to not being on a live server. I personally (and a lot of the community agree) think that players should be able to save their maps, prefabs & game types locally. Now I’m not going to leave you with the idea and not tell you a way that this could possibly be done, so keep reading 
Implementation - Now this isn’t going to tackle the entire issue because I’m not a developer, and in truth have no idea how this could/couldn’t work, but a good way with how this is implemented would be to allow players to “opt in” to reserving specific amounts of space on their storage devices. Not idea how much data is in a memory full forge map but that would be the best way to start looking at what you can provide players.
Think Halo MCC, you can pick and choose what parts of the game you would like installed but this time your not taking away data, you’re reserving it.
Let’s say a totally memory full forge map is 500MB, give players five different size options to reserve local storage for maps, prefabs and game types with the first option for people being that they do not wish to save their files locally, so they “opt out.” The second option may be for players that may not have a great deal of storage on their console/computer but still wish to save a small amount of their content, this being 2GB, the third option being 6GB, the fourth being 8GB and the fifth being 12GB for people who often don’t have consistent access to Xbox live servers or poor connectivity but still wish to save their content for themselves.
Now this would all be great, but I bet you’re wondering hmm so what if this player now decides they want to share their creations online. Well yes, this is obviously going to require connection to Xbox live, but give players the option to “upload” this content to the server browser. Think of previous Halo file shares (besides Halo 5.)
Conclusion- Local saves and the option to upload those files give those players a choice to either share their files or not while also allowing them to forge free of desync and other connectivity issues that wouldn’t effect them if they were forging alone or offline anyway, it also allows them to save their creations or upload them at a later date if desired.