After you publish your File Upload Form form, the website hosting the form may show an error that reads:
Unexpected strict mode reserved word (line 922, file "forms.studio", project "FormsApp")
This error likely happens when you switch your Google Apps Script project to use the Chrome V8 engine which is currently not compatible with Google Forms library.
To resolve the issue, open your Google Sheet associated with File Upload Forms. Go to the Tools menu and choose Script Editor.
Inside the Script Editor, go to the Run menu and choose "Disable new Apps Script runtime powered by Chrome v8"
Next, go to the Publish menu inside the Apps Script Editor, choose Deploy as Web App, select a new project version and click the Update button to publish a new version of the web app in Rhino mode.
Open the form URL in a new browser window and the error should no longer appear.