Epicor ERP Hanging Issue

We are using Epicor 10.2.400.28 . Our 4 to 5 Plants are using Epicor. Our server is centralized and rest units are connected with fibre & RF. We are facing Epicor hanging issue daily basis. When someone is posting AP Invoice and generating legal no, System hangs and entry does not save and at the same time When Store user Issuing Material, it hangs and Production is posting jobs, it hangs. at this time , Nobody can save his entry. Some time this problem resolve automatically and some time it does not solve for long and user have to wait or we have to recycle IIS application Pool . Please guide how can we remove this problem permanently and how can we find the root cause of this problem?