Please, send it to someone who has experience of chequering.
There's about an hours' work there for an experienced chequerer, so it won't cost the earth - but to correct a job where someone has, 'had a go', could cost more than double.
Following a line is easy - maintaining depth and cut direction isn't - neither is selecting the correct cutter angle to suit the LPI, which nobody has mentioned.
Borders are not put on to hide overruns, it's a myth. They obviously can be used in this way but a neat, double or mullered/English border is more difficult to cut than the chequer itself and is a sign of ability, not to hide an overrun ( which can be corrected in a number of other ways ).
If you were closer, I'd do it for you but you're not exactly local sadly.
Cleaning up a infilled chequering pattern with a dulled, single line Dembart cutter is fine - but that needs a correct recut and should be left to someone with experience. Trust me, I have several stocks in for attention right now, all from someone, 'having a go'.
Best, Craig