If a underground substation is deconstructed it yields a regular substation instead.

This can be further exploited by converting the substation to a underground substation in the EMP.

essentially giving access to unlimited quality materials with the use of mods like recursive blueprint.

Thank you very much for reporting the issue. Version 1.21.1 has been uploaded, it should resolve the issue.

As for the exploit, I guess the solution will be to change the recipe. The intent was to make them interchangeable, but that is directly exploitable as you pointed out.

Version 1.21.2 has been uploaded, changing the recipe for the underground substation. This should resolve the EMP exploit.