@abhishek_solank Amazing, thank you so much, this solved the issue!  The custom field is now syncing: Not sure if I updated the regex correctly, but it now looks like this (I added the two periods (.)): "^(u_|[a-z$.])([_]?[a-z$.\d]+)*$" Since it works I'm not gonna go searching for trouble 🙂 Best regards, Andrew ... View more