You face an issue where a till sometimes doesn't batch and it keeps happening regularly. You batch all the tills at the night and get a Polling Report email the next morning saying a till has not been batched although you had no error messages displayed.
The issue is most likely caused by a network connection that may have disconnected during the synchronization attempt. For this, you can consult with your Network team and see if they can assist with the possible network failures.
As this seems to be connected with the network connectivity, in terms of the intermittent successful batch, it is suggested consulting with the IT team should such issues arise.
If you have checked with your IT team and the issue does not seem to be on your side, raise a support ticket including any information on the error and the faulty till and the Prologic support team will be happy to assist you.