Paintwork can sometimes appear to ‘bubble’ and then eventually chip/flake away from the surface. Leaving the painted surface uneven and unpleasant to look at.
The process of paint blistering and flaking occurs due to poor adhesion. This could be due a number of reasons such as painting a surface that’s wet/damp, painting in high temperatures, moisture seepage and insufficient surface preparation.
If the blister/flaking goes down to the substrate, then moisture is likely to be the cause of the problem. You should remove all loose paint, down to the substrate, with a scraping tool and then use a suitable abrasive paper/tool to smooth over flaking or rough edges.
If the blister and flaking appears to be just of the top layer(s), but not down to the substrate, remove the paint from the affected area and then lightly sand down the surface edges to ensure the finish is left smooth.
Once the problem area has been removed, the area needs to be cleaned and dried before reapplying the coating.
You must always investigate the cause of moisture, as just simply reapplying the coating will not cure any underlying issues.