I had this problem too and manually changed the location to: /volume1/@appstore/Duplicati/SQLite-datafolder/RCTIOGLGOX.sqlite
Mono.Data.Sqlite.SqliteException (0x80004005): Insertion failed because the database is full
database or disk is full
at Mono.Data.Sqlite.SQLite3.Reset (Mono.Data.Sqlite.SqliteStatement stmt) [0x00096] in <62e44d67e13348a795e30fd7dd8622df>:0
at Mono.Data.Sqlite.SQLite3.Step (Mono.Data.Sqlite.SqliteStatement stmt) [0x00046] in <62e44d67e13348a795e30fd7dd8622df>:0
at Mono.Data.Sqlite.SqliteDataReader.NextResult () [0x00129] in <62e44d67e13348a795e30fd7dd8622df>:0
at Mono.Data.Sqlite.SqliteDataReader…ctor (Mono.Data.Sqlite.SqliteCommand cmd, System.Data.CommandBehavior behave) [0x00051] in <62e44d67e13348a795e30fd7dd8622df>:0
at (wrapper remoting-invoke-with-check) Mono.Data.Sqlite.SqliteDataReader:.ctor (Mono.Data.Sqlite.SqliteCommand,System.Data.CommandBehavior)
at Mono.Data.Sqlite.SqliteCommand.ExecuteReader (System.Data.CommandBehavior behavior) [0x00006] in <62e44d67e13348a795e30fd7dd8622df>:0
at Mono.Data.Sqlite.SqliteCommand.ExecuteNonQuery () [0x00000] in <62e44d67e13348a795e30fd7dd8622df>:0
at Duplicati.Library.Main.Database.ExtensionMethods.ExecuteNonQuery (System.Data.IDbCommand self, System.String cmd, System.Object values) [0x0004e] in <118ad25945a24a3991f7b65e7a45ea1e>:0
at Duplicati.Library.Main.Database.LocalDatabase.Vacuum () [0x0000c] in <118ad25945a24a3991f7b65e7a45ea1e>:0
at Duplicati.Library.Main.Database.LocalDatabase.PurgeLogData (System.DateTime threshold) [0x00072] in <118ad25945a24a3991f7b65e7a45ea1e>:0
at Duplicati.Library.Main.Operation.BackupHandler.Run (System.String sources, Duplicati.Library.Utility.IFilter filter) [0x0082a] in <118ad25945a24a3991f7b65e7a45ea1e>:0