So I have a Naniwa Pro 1K P-310. I had it stored in my sharpening stone holder (the standard type with rubber holders and two screw nuts on the one end) and when I removed it to soak I noticed it had warped. When I put it on the counter top it would rock corner to corner. This was not a case of needing lapping. Soaked it and used it anyway. I wondered if it was the pressure from the holder so I left it to dry flat on the counter. Next time I went to use it it was flat again. I didn't think I had the screw nuts on the holder really cranked down, but who knows. Has anyone else had this happen?