Hey @alfiofer here's a link to the owner's manual in Italian https://www.fmicassets.com/Damroot/..._Rumble_Studio_40_Stage_800_Rev_A_ITALIAN.pdfSo turning off wifi should fix it...
I'm very interested in the Studio 40 myself and have been reading through the owner's manual. As far as the Wi-Fi goes, it sure looks as if you are only to have it on when doing updates; making programing changes and other selections. When you're done with that you turn it off to play. That isn't stated that way specifically, but it seems to be inferred.I can’t say with certainty, but I turned it off on mine and have not had any issues.
I've only auditioned a Studio 40 one time for about an hour and had absolutely no problems whatsoever.