As a hint you might dump the blocks out of those freed extents in the beginning of the segment and see what's really there.
I hope you will solve this as one of those 150.000 records inserted daily there might be one "mine". ;-) So I hope you won't run out of space on "my" row.
Anyone out there has a solution or work-around for this type of situation.
-- Best regards, Alex Gorbachev