I have had players complain before that when they go to builder, sometimes it resets their build to level 1 and i have had the same experience now several times in my solo play. Clicking away and re-entering from the character selection screen usually allows me to restore the character to the last expected state.
I have encountered this with Daggerheart characters as well. I have also then redone the character leveling, only to not see it immediately when returning to the character sheet. Reloading the tab generally then updates it correctly. So perhaps something is going on with the retrieval/cache system?
Can the impacted users log out and log back in? If this doesn’t resolve the issue, please let me know.
I regularly lose levels (not all the way to 1st, usually just the last level), and it seems to be related to browser vs server storage. Most of the the time I can fix it by refreshing the page before changing from builder to sheet (or vice versa), but not always.
Another “fix” is to copy the link to your character from the “share with link” option in the sheet character settings then use that if you need to get back to the right place later.
Finally, clearing your browser data seems to work, too.
Hopefully they find out why this happens.