I had just rebuilt my road down to an iron ore mine, and upon removing the extra road (layout was wrong for my city build) they now don't go to the 2x supply depots I have available but straight to one of the mining depots. Even if I remove and rebuild the road, they still insist on going to the mining depot for pickup.

And now only send 1 drone at a time :(

Further to this -- I ended up building a supply depot and belting everything over, they started working normally again. :/

I am not really sure of the issue, can you send a save game showing them not working properly?

Sorry - as it was my only supply at the time I fixed it.

All I can say is a friend built a road using Contruction Bots to an iron ore field. We had 2 miner depots extracting into a warehouse then into a supply.

When I needed to expand the base in that same direction, the city block road layout I'm using didn't match so I built a new road down, and then removed the old one but no matter what I did the drones decided they wanted to pickup from the mining drone hub only (and 1 at a time at that).

If I replicate it, I'll share again.