not sure if this is related but next 15 has breaking changes for the properties like params https://nextjs.org/docs/app/building-your-application/upgrading/version-15#async-request-apis-breaking-change

you can either downgrade or try to await the params like this:

type Params = Promise<{ slug: string[] }>

export default async function Page({ params }: { params: Params }) {  
  const { slug } = await params
}