Possible reasons for gaps between ceiling and walls.

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examples..

We have lived in our newly built home for approx. 2 years.  The first winter, we found a gap - where it looked as if the ceiling was separating from the wall.  We communicated this issue to our builder and was told that this was a common, normal occurrence.  Each year, the builder has come out to fix and has communicated that this will continue due to the change of season.  I have never seen this before - and have built in the past - and never experienced this.  Nor have any of my neighbors or friends seen this in the homes they have built.  Is this common and can this be permanently fixed?  Thanks!
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Is this a drywall joint that is being re-taped and filled at each repair? Season changes should not cause this. Settlement perhaps. Two story house? Maybe foundation shifts.