Squadron White putty flaws

Two days ago, I filled the one side of my S13's sideskirt with squadron white putty, to give the thin styrene a strong base when polishing the paint. When I looked at it yesterday, the putty had eaten through the styrene! Has anyone experienced this before? And why wasnt I aware? I just figured it would be fine with the styrene.

I dunno, i use squadron all the time. Thats the putty i used on my Camaro

Two days ago, I filled the one side of my S13's sideskirt with squadron white putty, to give the thin styrene a strong base when polishing the paint. When I looked at it yesterday, the putty had eaten through the styrene! Has anyone experienced this before? And why wasnt I aware? I just figured it would be fine with the styrene.
Squadron putty belongs to the solvent putty category, and solvent putty is supposed to melt plastic to blend with plastic. That's why solvent putty is used for gap filling and sink mark correction. If you use it too much, it might as well melt plastic. What you should have used to reinforce the styrene was epoxy putty or polyester putty.