My Gill deck shoes were completely losing their grip. We are talking scary-slippery, to the point I nearly went on my ass, and overboard was a real possibility.
We have seen this before. Seems like whatever material deck shoe soles are being made of these days, it develops a hard yellowy layer way before the shoe is worn out—shoe on right.
We have tried sanding before, but with not a lot of success, so this time, in desperation, I took a grinder with an 80-grade disk to them—shoe on left.
That fixed it, as grippy as new.
Keep at it until the yellow is gone and wear a respirator, I can’t imagine the dust is good for us.