Printing Lines to match on both sides of the paper (A3)

[ExLibris]

Hi there, I am hoping someone on this forum can shed some light on a technical problem I am experiencing when trying to print lines with my inkjet printer.

I need to print lines on both sides of a sheet of A3 size paper (for notebooks I am making).
I need the lines to match precisely on either sides of the sheet of paper. Each time I try to achieve a correct result, the second set of printed lines on the reverse side of the sheet is printing 1 or 2mm off – it is very inconsistent.

Any suggestions would be appreciated!!