Fixing drywall tape that bubbles up

When drywall tape breaks loose with a little bubble, it is because there was not enough compound under the tape when it was first put on. If you can, lift the paper ever so little with a spatula and then simply slide in some fresh drywall compound to glue it back down. In some cases, white glue might work, with a little masking tape to hold it in place until it dries.