SAP B1 slow processing when items managed by serial

Hello to all,

We are managing items by serial numbers at our two clients. Both are facing slow processing problem.

Whenever any user processes any transaction for serialized item, all SAP users get stuck and sometimes caused "SAP stopped working".

One client is on SAP B1 9.2 PL04

while other is on SAP B1 9.1.

Both are on SQL.