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.
Thanks