Recurring crack in the ceiling

We have very recently repaired 2 cracks in the ceiling of the second floor in a 45 year old home. One crack ran between two AC registers, and another ran from a corner of one interior wall towards the center of the ceiling. I looked up today to find the cracks re-appearing in the same exact spots.
We spoke to the contractor who did the original repairs, and he is going to come and take a look tomorrow. He said that in the best case, he can put some braces between the beams in question and redo the ceiling there, and in the worst case, he'll have to put up new sheetrock.
My question is: are there any other options? I read somewhere that it's possible to put ceiling tape to help prevent the recurring cracks.. Is that reasonable? Is anything else possible?
Thank you very much! Elana

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