I am currently programming an alternative-specific CBC exercise, with 6 attributes, and quite a few prohibitions between some of the attributes. I have already programmed this, and the design was not deficient (not as efficient as one would probably like, but no warnings came up at any point). I was then asked to change the order of the attributes so that for instance attribute 3 would appear first, followed by attribute 4 and then attribute 2 etc. I made these changes and checked that the prohibitions are correct (and have not changed since my last working programmed version of the exercise), and generated the design (300 versions, random generation method).
To my surprise, the design was deficient however. Is there a reason why this would happen? Are there any specific circumstances where this might be more likely to occur?