TL;DR
When a bot emerges from a roboport, flies a bit and then needs to recharge it should never return to that roboport.What?
When a bot emerges from a roboport, when it's turned from an item into an entity, record that roboport as the last roboport the bot charged at.Why?
As can be seen herebots emerging from a roboport will sometimes return to their starting point. At which point they get that roboport set as "last charged at" and repeat the exact same flight path they just did but then recharge somewhere else the second time.
Please reconsider that this is not a desired behavior. The "last charged at" field in the bots was introduced to prevent just this looping behavior and seems to be unterutilized here.