The FormWizard throws an error "TypeError: Cannot read property 'get' of undefined" on edit pages in the Wikipedia namespace. For example: https://en.wikipedia.org/w/index.php?title=Wikipedia:WikiProject_Women_writers/Missing_articles&action=edit§ion=2
@Edokter first reported the issue, almost immediately after @I_JethroBT turned the gadget on by default for all logged-in users in the Project namespace. Description here and in the here.
@Jephpaul has looked into what might be going on, and we believe that the cause of the error is that mw.cookie() is not available on edit pages.
The FormWizard (code) uses a cookie to store the post-edit feedback message that is delivered to users once they create a page.
We didn't see this error before because we were using a built-in JQuery cookie function until @Mattflaschen recommended switching to mw.cookie during his code review (@T94595).
I'm not sure to assign this to, given there are no engineering resources allocated for this project. But I'll orchestrate the updates to the gadget, once we've identified the issue and know how to fix it.