Im afraid these dishwasher dont have any tension adjustment as the spring in the hinges are preloded so cannot be adjusted.
Now this can be repaired but you will need to replace both door hinges and fingers crossed that should do it.
But ive seen this fault a lot were someone has fallen on the door but its not always just the door hinges. Sometimes the innder door skin can bend at the bottom and sometimes this also needs to be replaced. But you wont know if this is faulty untill you have stripped it down and remove the door panel to check it.
Its a 50/50 change if its just the hinges only. Or both the hinges and the innder door skin.
But they can both be replaced so thats not a problem so theres no need to replace the dishwasher.
Now there is a option Neff do. Its a 12 month warrenty and the first time fix for about £16 a month roughly so for that price it may be better for them to do it. As its a complete strip down of the front and the hinges and inner door skin are quite expensive on these.
But this can be repaired not a problem. If you need anymore info just get back to me.
To get the part numbers and the diagrams click the link below and enter the full model number in the search box and it brings all the exploded diagrams up with the part numbers as well.
As to the neff warrenty it applies to all Neff appliances no matter the age. Its done through domestic and general. You need to ring Neff customer services on 0344(###) ###-####and they will talk you through it.