Yep, been there & done that. Anyone who's done any amount of painting has painted over existing paint at some time or another. Your issue illustrates the chance we all take by doing that. If something was wrong with the prep/application of the topcoat you're painting over, your paint job will fail too. It's one of the hazards we face for not wanting to strip every job.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.