After the latest Chromium update, our signTypedData function broke. Users started seeing the error shown in the screenshot, and the extension console looks like what’s shown in the screenshot. The issue gets resolved when users toggle OFF Settings > Experimental > Improved Signature Requests.
Additional info: We discovered that changing the name of our primary type from ‘Permit’ to anything else stops MetaMask from throwing this error. Even though Improved Signature Requests toggled ON
I recommend reaching out to the MetaMask support team for this issue so they can look into it.
In order to do this please visit https://support.metamask.io/ and click on the large blue “Start a Conversation” bubble located in the middle right of the page. A live chat bot will appear on your screen. It will give you an automated response at first, but afterwards you should be able to contact the support team directly.