Thank you for your investigation.
I overlooked the mining bonus.
It seems I'm still not proficient enough with Factorio.
I'll play the game more to become more familiar with it.

Thank you for your reply.
Save data attached.
You will be able to reproduce the reported phenomenon by picking up the electric mining drill next to the character.

Reproduction Steps:
Place an Electric mining drill and start mining resources such as copper ore.
Connect a belt conveyor to the output of the Electric mining drill.
Intentionally clog the belt conveyor to prevent resources from being transported out of the Electric mining drill (e.g., block the end ...