Our customer has a syncable feature service that is used to download a SQLite .geodatabase file for use in Runtime, with users being authenticated through AGOL and passed through to the ArcGIS Server service. This has been working as designed, but they have now introduced federated user ids that include each user's email, and the @ sign appears to be causing issues.
If I query the layer through the ArcGIS Server endpoint, I get the results as expected that include the @ symbol, so I know that the records are in the database. In the geodatabase file that is created on my local drive, however, none of the records are there for usernames containing the @ symbol. I deleted my previous local replica and verified that a new one was created and downloaded from the AGS instance. I have their admin looking for messages in the server logs, but the process appeared to complete normally.
Is the @ symbol in some way a reserved character or otherwise causing those rows to not be downloaded?