@philcottie,
Hi philcottie
I had the same problems as you with the newer Lovatts pens. I have always done as Dutchy does, photocopy and then transfer to grids.
I have bought Papermate eraser.max pens, used to be able to get from K-Mart but not always in stock.
Am now getting from a stationary supplies shop. they keep saying Papermate are not making erasable pens anymore but if you search you may find them
Good Luck