It is probably a bug in the handling of the data stored in the windows registry created by older versions of Preform. I deleted HKEY_CURRENT_USER\SOFTWARE\Formlabs. After that Preform does show the dialog only once.
A new key named DataCollectionConsent is created which stores data which was previously located in NetworkLoggingRegistry. If you dont want delete the whole Formlabs key it is probably sufficient to delete all entries of NetworkLoggingRegistry.