WinScriptLive will never "change" anything in a script "automatically". So if you have an older version of the product file that works, it will be saved forever with your .ami script file.
To use an edited product file, you must either make a new script, or re-load the product file into an existing script. WinScriptLive does re-load all of the product files on boot, but it doesn't copy over your original product file for that script.
Basically, the script's product file needs to be refreshed. If you change the "version" number near the top of the product file, WinScriptLive will automatically ask you if you want to update to later version.
Otherwise, you just need to go into the "edit" screen for that particular device (in the "devices" screen) and select your new version.
Note: Be sure you don't have two files different name (such as MyProductFile1.prd and MyProductFile2.prd) but containing the exact same make and model (such as Make="Christie" and Model:"Projector")