See attached image. I don't know what this is. I tryed to undo last changes (nothing unusual; some variables, custom forms), also loading previous specifications, plus more last hope guessing like rebooting the engine and my machine.

Did you define a "NameType" in your data definition of your specification?

I haven't defined a "NameType", so this error was very strange. However I was able to go over it making a new better specification