A script error is usually related to the Javascript or code functionality. Something inside the program is not working properly or the files that you have sent contain invalid items and the software gives you this script error.
Also, take note of the script error, its code and what it means then simply use Google to look for an answer. Additionally, contact the developers of the BIR application. As far as I know, they are from the government since the forms are for accounting and finances purpose.
