Are you referring to the tape joints in a sheetrock ceiling? If so, how are they reappearing? Are the joints sunken, pronounced, or coming loose? Or perhaps stains are bleeding through?
...As a painter there isn't a lot that can be done for poor drywall work other than to apply the most forgiving flat paint possible and pray...If you have drywall experience you can attempt to rectify the matter by refilling (sunken), building out (for visible humps/joints that were neglected in the sanding phase--A curved trowel sometimes works great in these situations), or, if it's slight, a retexturing...If the ceiling is smoothwall, good luck to you, especially with a revealing light source, every flaw is exaggerated and you're looking at some sleepless nights...
...Now if you're NOT talking about drywall tape edges, then...nevermind...