A. Technically speaking, yes, cigar humidors should be as air-tight as physically possible. When I came into the cigar business, someone told me about a "the dollar test;" if you couldn't slip the edge of a crisp dollar bill in-between the lid and the base, the humidor had a good seal.

Another method is to open the humidor and place the dollar perpendicular to the edge (as you would feed it into a vending machine) so that half of the bill is on the inside and the other half out. Close the lid, then try to pull the bill out of the humidor. If the humidor has a good seal it should be very difficult to pull the dollar out short of tearing it. Moreover, this test should be done on all four sides of the lid.

In your case, the bigger question should be: despite the gaps, is the humidor keeping the cigars fresh? If your box is within the "normal" range 65-75 degrees x 65-70% RH, then I wouldn't worry too much about the gaps. If the gaps are exceedingly wide, they will cause problematic variances in your temp & RH. Make sure you have a good digital hygrometer/thermometer to monitor the conditions in the humidor, too.

Finally, if the humidor is brand new and the seal is noticeably out of alignment, return it.