Mine does it to a small extent but there's always at least 2mm of edge.

You know when you insert the source (left) spool, you need to rotate it a bit so that the bottom spindle clicks in properly... maybe that's not happening and the spool is therefore offset slightly?

When it's freshly loaded, how does the paper sit on the pressure plate? Centred? Put the insert in the back and check to see if the paper is properly covering both rails on the gate.