Sand are coming off from sanding block when wet sand?

-Sand start coming off from sanding block when wet sand.Does it mean I need a new one? But this sanding block is not old.-I use tooth brush to clean i

-Sand start coming off from sanding block when wet sand.
Doe's it mean I need a new one? But this sanding block is not old.
-I use tooth brush to clean it, is it harmful to the sanding block?

or:-Sand start coming off from sanding block when wet sand.Doe's it mean I need a new one? But this sanding block is not old.-I use tooth brush to clean it, is it harmful to the sanding block?

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