Hello Thomas Staehli:
Thank you for posting.
I was able to replicate your issue when hosted by FileMaker Server. I am forwarding your post to our development and testing department.
I too am experiencing the same issue using a filter with the ≠ condition.
From earlier reports with 12.0, I'd guess that <> does not work either. Correct?
Opening a new bug report record specifying this issue in terms of FMS 12.
I've just tried to replace with field <> 0. All the records with field = 0 appear (tried on 12.0v2)