When you bind off on the purl rows, purl the stitches that you are binding off, but when you bring the stitch over and off the needle, keep your yarn in back, then bring it forward to purl the next stitch. I'm not sure it this will solve your problem, but it's worth a shot.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry