Here is a workaround for the problem: https://bugs.kerbalspaceprogram.com/issues/23172#note-19
Edit both your persistent.sfs and GameData\SquadExpansion\Serenity\Resources\DeployedScience.cfg and increase the value ScienceTimeDelay from 60 (one Message every Minute) e.g. to 21600 (one Message every Kerbin day).