"Independent" verifiers are nice, but they can be compromised. There's nothing from stopping the DNC from paying some goon to walk in, say "everything's legit" while watching a poll worker burn ballots and snort the ashes, then walk away.

The only solution is to have multiple parties verify the results via observers. Dem, Republican, Libertarian, Green... EVERYONE. And the Dems are blockading efforts to have observers watch the recount because they know this will destroy them.