Hi, welcome to Just answer
Please tell me its complete model number
and how old is it ?
ZWH 6130P. Purchased 16.09.2013
have you tried to clean the drain pump assembly ?
Is that the same as the drain filter? !!!
Yes and also the drain hose?
No, I haven't tried that. Is it correct that the drain hose needs to be positioned higher to also help prevent water coming back into machine?
Yes, you can also check its User Manual here