Asus 20B1LT lightscribe problem

[qanda]This thread is about the Asus DRW-20B1LT. Click here to see full specs[/qanda]Hi,
My pioneer went belly up so I replaced it with this. Burns fine and recognises lightscribe, but at the end of printing there is just a very faint pinwheel effect. I upgraded the lightscribe software and tried a few different burning software but all the same results. Can’t find any firmware upgrades so not sure what else to try.
Media is verbatim and worked fine with the pioneer.