When starting the app in debug mode I'm now getting this error message:

Error: The placeholder, count, has its "type" resource attribute set to the "null" type in locale "en", but it is "num" in the template placeholder. For compatibility with template placeholder, change the "type" attribute to "num".

Unfortunately I have no idea how I am supposed to address this.

Do I need to go through the arb files and check every single entry if it has the exact same shape across all languages?
Because I don't have any types or anything set anywhere explicitly, I just have a bunch of arbs.

I think this problem started with the 3.29 release.

I have already tried removing generate: true from pubspec.yaml and adding synthetic-package: false to l10n.yaml.