I am used to American 2N3904 and 2N4401 transistors that have datasheets showing their max saturation voltage with the base current 1/10th the collector current.
The BC107, BC108 and BC547 European transistors have 1/20th on their datasheets.
The BC108 has a max saturation voltage of 0.25V when the collector current is 10mA like yours and a base current of 0.5mA. Your base current is more than twice as high but your saturation voltage is higher than it should be so your transistor is damaged maybe by avalanche breakdown before.