LEAK TEST PROBLEM

Hello, help me with this in my laboratory we have a "ELEMENTAR VARIO MACRO CUBE" which is used for reading organic elements the problem is that when doing "rough leak test" the helium pressure exceeds the limit of 20mbar so it may be a leak the thing is that I have already tried everything I can reach as cleaning the parts, closing the valves well but I can not find the problem, please help me with ideas. thank you very much.

Equipment: elementar - vario macro cube