It is not uncommon to find areas with loose paper drywall tape, especially in homes or buildings with high ceilings. Often, tapers will not do more than one coat of compound at the peaks in rooms, and in a few years it becomes noticeable. To fix this problem, the first approach, in most cases, is to cut the tape vertically too allow compound to be put beneath the tape and squeeze out any excess for a flush coat. After drying, one or two more coats of mud/compound can be applied.
  Sometimes there are wavy or bubbly looking seams that can either be remedied with more joint compound or tearing out the old tape. It can be replaced with either the fiberglass mesh tape or paper tape with holes in it, or regular paper tape. I prefer the fiberglass for strength and ease of use (squeezing out excess compound), and frequently only needing 2 coats of mud to complete the work.
  Durabond powder mixes also speed up repairs with cure times of  45, 60, or 90 minutes, most commonly. They allow one day repairs when time is a priority. The only drawback to Durabond is you're not supposed to paint it. So at least one coat of joint compound needs to be applied, then sand, prime, and finish paint.
  For most people / DIY'ers, using the compound in the blue and white tub is better.  The green and white pails work fine but tends too shrink making additional coats and sanding necessary. The blue and white or dust control type does contol the dust and makes less of the nasty drywall dust. It amazes me how many people don't use dust masks when sanding compound since it really is not good too breath as well as getting dust all over a house if plastic is not put up between rooms. Anyway, just trying let people know a few things about working with compound.