There are breaking changes in ink! rc-9. Some of them are effective even if you're not using rc-9. Don't know if this is known to you.
https://github.com/paritytech/ink/blob/v3.0.0-rc9/RELEASES.md
One of the changes is about the dependencies of scale. The dependencies should be updated as below:
scale-info = { version = "2", default-features = false, features = ["derive"], optional = true }
scale = { package = "parity-scale-codec", version = "3", default-features = false, features = ["derive", "full"] }