I purchased this unit to install at my mother's house.  I have used GiffGaff and O2 sims, both of which log in to start with but very quickly disconnect. If I am lucky then the system reconnects to the 4g network, if I am not it just simply whirs merrily to itself.  Is this an O2 issue (giffgaff being an O2 network), is it a duff unit or is this normal for the use I am expecting to put it to?

I am currently running a mobile phone with hotspot, and that works a treat! Do I cut my losses and return the unit?