Had the same issue when using custom defined shadcn components.

I was also getting another issue to do with the .

Fixing that means adding "module": "preserve" to tsconfig.json. It's required by "moduleResolution": "bundler"

That change refreshed the Editor (VS Code), fixed the script issues, and fixed the @render error too.

Please read more into the change v5 change from slots to snippets because the change also has some quirky edge cases: https://svelte.dev/docs/svelte/v5-migration-guide#Snippets-instead-of-slots