Probably debris jamming it try leaning machine back against wall at 45 degrs then twist filter forward and back repeatedly this should make debris fall back in and filter can open. If this does not work you will have to dismantle the pump. Get back to me if you need instructions to remove pump.
Kenjo
April 2012
I can answer this question...
The flter on my Boschxx 1400 washing machine will not unscrew?
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