Hi @Luca_Lattarini ,
In DTM, an Analytics beacon is fired on every page when App Measurement loads (Analytics library), even if no rules have been defined. In Launch, this beacon call is controlled by a rule and does not happen automatically. The upgrade process creates this rule for you unless you use the Page code is already present option in DTM. This rule is called "Migrated from DTM: Adobe Analytics - Send beacon on every page".
The Upgrade Assistant creates this rule in Launch, as long as an Analytics tool is installed in DTM. If you used a return false inside custom code in DTM to suppress the initial beacon call, then you should leave the Launch rule out of your library (or delete it) after the upgrade is complete.
Thanks!