Hey Thanks Guys! I also think that we need to share experiences here.
I got answer from help desk that problem could be bad ground.. I checked all my elec. cables and the one I was using in FOH was broken.. Sometimes it had ground, but when in right position it lost ground.. So have to check cables at least 2 times in year 
But I think this was problem because I never had any bigger problems with table.. And A&H support was also very fast with answer. Thanks.
