My configuration differs greatly from yours, but I'll comment on a somewhat similar difference.
In my case I have a Davis VP2 reporting from the console to my PC running original Cumulus through a Davis dongle.
Sometimes my PC is not downloading the dongle continuously (I forget to restart Cumulus after doing a maintenance exercise, most commonly). After I restart Cumulus it downloads the missing hours from the dongle, but for those hours the gust peaks are materially different than they are for the hours when Cumulus was watching the data live.
Not everything that looks at peaks is recording the same way.