My elgi ultra wet grinder is almost 9 years old, still working ok. But I feel than nowadays it us not as efficient as before. For eg: I need to manually scrape the sides and push the urad dal to centre almost continuously and even then some whole urad dal remains in the batter. Also, grinding takes longer time. I was wondering if my grinder requires some maintenance. Do the stones need to be made rougher or some part needs replacing?