Did we look into this one at all? https://github.com/garden-io/garden/issues/5142
Since this a is Mutagen error but the builds are failing, I'm assuming it has to do with syncing the build context but not sure though.
I've seen this same Mutagen error intermittently but we should at least validate that this isn't happening consistently (if we haven't already) since obviously the Quickstart needs to work.
Also, we need to update the Mutagen binary. There's a chance that helps with these errors.