The appearance of swelling zones of the old coating, due to solvent penetration.
- applying too thick layers of primer,
- wrong amount of thinner (HS primers)
- too thick first layer of primer,
- too short a drying time,
- insufficient drying of putty or primer,
- the transition between the buffer and old coat was not properly sanded.
- make solvent test,
- isolate with the use of twocomponent primer applied with several thin layers with keeping time for thinner evaporation,
- avoid sanding topcoats.
Sand and apply coat again.