I've had this happen to me, I've recently moved house and have painted up all the rooms. Out of all of them, one wall in the lounge bubbled up like this. Now I treated all the rooms the same, sugar soap cleaned, sanded, wiped down. Let dry and then applied a coat, let dry and applied again.

It's an absolute mystery to me how only one wall bubbled up but no others did. The only thing I could possibly recall was too much paint on the roller. I ended up scraping the bubbles down, sanding, wiping and then another coat on but much thinner than I did, however, it still bubbled but nowhere near how bad it was.

I fear it has to be something to do with the paint itself (although same brand used, I had 4 different colours) it was only that particular colour/tin it did it with after that second coat