Gardener store fails to target garden clusters (virtual garden)

[networkhell]

Current setup:

OS: macOS 15.4
shell: fish, version 4.0b1
switcher: v0.9.3

I confgured my garden store like this

- kind: gardener
  config:
    gardenerAPIKubeconfigPath: "~/.kube/kubeconfigs/garden-dev.kubeconfig"
    landscapeName: "dev"
- kind: gardener
  config:
    gardenerAPIKubeconfigPath: "~/.kube/kubeconfigs/garden-staging.kubeconfig"
    landscapeName: "staging"

In general it works as expected and I am able to target seeds and shoots. But the discovery of the virtual garden contexts fail with the error messages

25R250000] failed to write alias dev-garden for context name dev-garden  store=gardener
  38R380000] failed to write alias staging-garden for context name staging-garden  store=gardener

I have no idea how I can further debug this issue. Are there any naming constraints?