Hi not sure is bug or part of the mod, but there is plenty room left for resources but not all the drones placed in depots are being used?

Can you provide a save game?

i do have the same issue:
https://1drv.ms/u/s!AlduFs-osXHvjCli1QXnCdjLaHUX?e=XlLNrw this state in non working condition
As for me it starts happening some time after I refill the lost drones (to trains, maybe i should better protect them from the trains) from the logistic network.
https://1drv.ms/u/s!AlduFs-osXHvjC3RiKmezdMeHrm5?e=6ubhfL here are the save state before i started resupply the mine and one after starting resuppling still in working condition. if I remove the drones from the mine and refill it, it starts working again.
Using mod version 0.3.9

Thanks for the save games,
I managed to figure it out, its fixed in the latest release now