Certain words, phrases and characters are not allowed as parameters and script variables. For example, numbers and spaces are not allowed as variables. Underscores are allowed, but not recommended as separators of words in a variable. Instead, a best practice is to use a capital to denote separations in a variable name. For example, a variable may read CouchCushions or Couch_Cushions (less advisable), but never Couch Cushions or Couch-Cushions.
Certain words are also not allowed as a parameter variable. For example, SHADOW can not be used as a script value, because it is a script command. This is one reason I use all caps for script commands and lowercase text for values. See General notes for more information.
For this reason I recommend checking scripts often. Some of the script warnings are a little cryptic for those of us who know little or no GDL, but with a little trouble shooting the solution is not far off if you check the script often enough.
A script warning for a saved object (rather than one written from scratch), is almost always caused by a value in a script that is not available in the parameters, or a value that is using non-allowed characters or text.