DC07 cyclone clogging
The central tube inside the DC07 bin has a tendency to clog, even the later modified version.
Ensure that the central tube is totally clear of fine, fluffy dust. It does build up very easily and is not readily discarded when the bin trapdoor is open. If it is very clogged, try using a garden plant cane, and a suction vacuum cleaner to clear it.
Don't use water, as you will have to ensure that the inner cyclones are thoroughly bone dry, else moisture might make it to the motor. Also, water and dirt form mud.
The idea of the fins in the DC07 bin, is to reduce the amount of dust becoming re-entrained in the upwardly rotating airflow, going to the perforated shroud. The fins therefore assist with improving the efficiency of the outer cyclone.