SQLite exception: Database is locked - sqlite

Question

I have looked into all the questions on the "database is locked" exception but none solve my problem. I have a static function in DBActions class that inserts a record in DB as follows:
public static class DBActions
{
// save col, value pairs in DB table
public static int SaveInDB(string table, string[] cols, object[] vals)
{
int resultID = 0;
string query = $"insert into {table} (";
for (int i = 0; i < cols.Length - 1; i++)
{ // leave the last column coz comma does not follow it
query += cols[i] + ", ";
}
query += cols[cols.Length - 1] + ") values (";
for (int i = 0; i < cols.Length - 1; i++)
{
query += $"'{vals[i]}', ";
}
query += $"'{vals[vals.Length - 1]}')";
//MessageBox.Show(query);
using (SQLiteConnection con = new SQLiteConnection(Global.ConnectionString))
{
using (SQLiteCommand cmd = new SQLiteCommand(con))
{
try
{
con.Open();
using (SQLiteTransaction trans = con.BeginTransaction())
{
cmd.CommandText = query;
cmd.ExecuteNonQuery();
resultID = (int)con.LastInsertRowId;
trans.Commit(); // raises the exception
}
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
finally
{
con.Close();
cmd.Dispose();
}
}
}
return resultID;
}
}
and I am calling this static function whenever I need to save some record in any table like this:
Global.StartTime = GetCurrentTimeStamp();
string[] cols = { "SampleID", "OperatorID", "StartTimeStamp"};
object[] vals = { SampleID, CurrentUser, Global.StartTime};
Global.ExpID = DBActions.SaveInDB("ExperimentSettings", cols, vals);
When I call it the very first time, it throws the "database is locked" exception. For all others, it executes fine. What could be the possible cause of this? I think all my DB objects are properly being disposed off due to the using statements.