duplicate records/not moving to uploaded

Using iRecord app on an android phone I sometimes press 'submit all', the uploading circles spin round for ages but they don't move to uploaded. I have been repressing 'submit all' sometimes it then prices to have uploaded twice. Or this last time I checked the iRecord website for 'my records' they are there already. But now I have to delete each record in the app 'pending' individually to prevent them being uploaded twice.

Not sure if this is a problem on my app, or the database/website or a bit of both?

Is there something I can do differently.