Servis 6005 washine machine leak from filter?

Whilst using the washing machine today, the filter came out at the bottom of the machine along with lots of water. Th filter is normally turned to remove it and has a black rubber seal around the turn knob. I have tried to replace it but it does not seem to want to re-engage.
The filter is made of white plastic about 6'' long with prongs/comb at the far end to collect debris. THere is no thread on the filter or the tube so I cannot see how this should re-lock. The black seal appears to prevent the filter from being pushed back in.
It strikes me asa bit of a poor design!

Can anybody help??