Conditional key change does not trigger (re-)fetch

[pke]

I have a hook that should conditionally fetch some data, when a user logs in.

For that I use a conditional key:

export function useWatchlist() {
  const { session, fetch } = useSession()
  const selectedPharmacy = useSelectedPharmacy()
  const {
    data,
    error,
  } = useSWR(
    session?.userId
      // DEV-1837: include selected pharmacy to invalidate cache key when pharmacy is changed
      ? ["/user/watchlist", session.id, selectedPharmacy]
      : null,
    (href) => fetch({ method: "GET", href })
  )
  console.log("session & user", session?.id, session?.userId)
  ...
}

However, sometimes, while the log has several lines with (same) session and user id filled useSWR never starts the fetch. I see like 40 log lines but not one time a fetch request performed (also logged).

Could that be a debounce problem? Too many updates flooding the hook?

At the start of the program session is undefined therefore the key is null. But this seems to work on almost all other places I use this pattern.