Riding with the bots will generate a lot more UDP data so if you are going to get drops due to congestion related issues, bots will do it (as will large group rides/races). Have you tried a reboot of your router, tried using ethernet rather than wireless and generally shut down surplus wireless devices (headphones, phones/tablets etc).
Zwift did make a change (see below) and this could be related however I would expect the drops to occur regardless of density of riders around you if it was this.