Because your Oaks don't have an internet connection for whatever the retry period is (a couple of minutes), they reboot into safe mode waiting to be reconfigured.
The solution is to change your board profile. In the Arduino IDE, choose Tools -> Board > Oak by Digistump (Pin 1 Safe Mode, Manual Config Only) and they should be fine. The Default variant, is the one that has the automatic network/internet reboot checks, whereas the Manual Config Only mode doesn't do any of that.