I do not know since but i discover that if you grap a lot of items with select all and drag them to cargo, the cargo will not be filled up 100% like in the old days. Now all items are transfered which will be fit in cargo and you need to redo on item to fill up the rest of possible cargo. This is a pain if you have for example 1 m³ Veldspar. SO its not getting loaded. Only if you do it without select all. In case of the delivery bot the cargo in station will be never be filled because of this behaviour. Fast solution could be a change to the bot not to use select all and drag instead maybe check volume and then decide if select all or item by item. I bet slav will find the best solution for.

BTW i have seen this behaviour on multiple clients and its not a bug in the bot.

I want to use the deliver bot again instead of manually fly the ore around.

Deliverer addon for miner was developed to transport drones/crystals between stations on the route of the miner. It is free addon to miner, never sold separately. You need collector, it will transport all ore or whatever you need to central station within X jumps.