It can be done without completely removing bellows from frame. I run a blunt knife round the join to a depth of no more than half the frame width, then pull out any bits of old tape that are loose. I slightly reduce the width of the strips of tape for the end fold, spread glue in the gap, and on the tape, then work the edge of the tape into the gap, fold over, wipe off surplus glue. Once all the end tapes are in place clamp the bellows, either between stiff boards in a vice, or under a heavy weight, and leave till the glue dries. Make sure you remove all surplus glue before clamping! If you aren't confident that no more glue will squeeze out then lay strips of polythene or cling film over the glued areas before clamping