Problem solved.... You are using acrylic varnish. The decal solution will react to the acrylic varnish, it is best to apply a lacquer gloss varnish eg Mr Color, Tamiya.... The decal solution will in some cases act like a paint remover as will the warm water.
You have done nothing wrong it was the method that was wrong, I suffered the same myself, but unlike you I had to repaint the whole thing as the solution ran amok...
Do not give up - you are in a learning area, I suffered the same problems a decade ago when I came back to modelling and my mistakes were about £100 a time with cast resin armoured vehicles and using the wrong adhesive which melted the resin - and as you can see I am still here and still to this day learning, I have yet to master buildings from foam board despite watching videos on YT, and lord help me when I finally start to tackle 3D printing.....
You have done nothing wrong it was the method that was wrong, I suffered the same myself, but unlike you I had to repaint the whole thing as the solution ran amok...
Do not give up - you are in a learning area, I suffered the same problems a decade ago when I came back to modelling and my mistakes were about £100 a time with cast resin armoured vehicles and using the wrong adhesive which melted the resin - and as you can see I am still here and still to this day learning, I have yet to master buildings from foam board despite watching videos on YT, and lord help me when I finally start to tackle 3D printing.....
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