Custom mode doesn't seem to work anymore

[vrad-exe]

I use this extension's "custom" mode in Firefox to override the user agent sent to Gmail to be Chrome, since Google arbitrarily locks all other browsers out of offline sync functionality despite it being supported fine. However, as of somewhat recently this randomly stopped working, with Gmail now refusing to enable offline mode unless I open the extension and select a Chrome user agent manually. I haven't touched the extension settings at all (except changing the Chrome UA to a newer version in an attempt to fix the issue), so I have to assume this broke with an extension or browser update.

This is the specific custom json I use:

{
  "google.com": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0.0.0 Safari/537.36 GLS/100.10.9939.100",
  "microsoft.com, office.com, skype.com, bing.com": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.0.0 Safari/537.36 Edg/114.0.1788.0"
}

If I copy and paste the exact same Chrome UA into the extension popup and apply it manually, it works fine