>>It isn't workaround but rather different way to achive the same result.
>
>Yes, I understand. It's just that I have UNIONs elsewhere and I would really like to know what caused that situation. If this is a known bug, assuming only one record in the Other table, which would cause this or something like that, I would have at least something to rely on.

Hi Michel,

I can see why you consider this a workaround. :)
Is record in Other table unique or is a copy of one of the records selected from Reserved table? You do know that UNION internaly does DISTINCT on all result records to eliminate duplicates?