Reubent cannot desribe it more perfectly. For self-assembled stands, issues like you have encountered are bound to happen. In most cases, the installation by the user is the cause (in screwing the plates to the vertical pillar) but sometimes minor flaws such as a slight uneveness at the edge of the vertical pillar will cause this 'skew' of 5-10 degress you are talking about. I think I get what you are saying right now. Quite a norm in self-assembled stands and won't affect performance too much.
Cheers.
Cheers.