Hello team.
We stopped supporting the plugin your project is using a while ago. You can read this blog post if you're interested in getting more details about this process, so it'll be difficult to know why errors may occur while using it.
We just released a new version of the recommended plugin (gatsby-source-prismic), as well as newly updated documentation.
We also have a dedicated migration guide if you decide to move to the new one:
I hope you find this information is useful. And if you migrate your project you can always contact us if you ever have any questions or need help with anything.
Thanks