If it was possibly down to the gypsum board as you indicate, just doing cyber surgery without seeing or inspecting , I would suspect it was possible dust from the original drywall; could also have been a combination of the dust with some addition of cleaner residue or paste residue from stripping the wallpaper. Not saying you were not thorough in your cleaning , etc. , but these are possibles from anyone. Paint failure doesn't have to happen immediately. It can come with more stress on the substrate at a later date (such as this instance).

As far as tape, I saw your other post. Frog tape IMO is not as good as the marketing hype it has gotten. I have used Scotch 3m 2080 delicate blue painter's tape for years and nothing beats it on the market for sale. Not all blue painter's tape are equal. Need to make sure you are buying the correct one.

As far as burnishing, you will get a much more closeness with a touchy feely method if one burnishes with their index finger really really firm. Placing the tape and lightly pressing in place and then coming back to seal and press really tight with your fingers. Taping blades or other objects can actually cut into the tape edge or make a ridge or make areas on your wall from the blade if not watched for the pressure or the angle of the blade.

If you had freshly painted your walls all over, then sealing the tapes edge line with the base color is the ultimate best solution for sealing. If the wall has been painted for some time (as in your case) you can use acrylic glaze , or a matte sealer, a flat varnish or the caulking as previously mentioned to seal the tape edge line.

When doing your stripe color, don't let the roller or tool you are using touch directly at the tape edge; instead run the roller or your tool over onto the tape a little. By rolling or using your tool and coming right up to the tape edge one runs the risk of seepage by pushing the paint under.

Another thing after pressing the tape down either with a tool or your fingers, it is best to seal if you are not going to be painting right away because with certain sheens , oil paint, or heat, the adhesion of the tapes edge is likely to come loose a little and you might not know it . Thinking all the time the tape is still secured and by sealing this will already help bond the tapes edge. This is when you can't get to the paint job right away.

It really shouldn't be a hard task to do touch ups with an artist brush and your base coat. You also might want to remove your tape as soon as you have painted your stipe , while the paint is still wet and hasn't started to set; otherwise if you wait until it has dried to touch to remove might need to lightly , (very lightly) score the tapes edge if it is pulling and removing your base.