Nah!

Probably got your hand oil on the slate. But the light sanding didn't fix that huh?

I constantly sand all my glass and slate calls.

Do look at your striker and make sure that is clean. Try different strikers. Thourgh use you do wear the edges out and you may need to re-edge them.

Take the slate and wipe it with a little alcohol and let it dry. That will take youhand oil off.

JW