The FU should make a call. The PU MAY overrule whether asked or not. A FU should never throw up their hands (figuratively) and say I dunno. Sell it then review with PU if warranted.
The 3rd base call. Depends on the length of time the fielder held on and if any action by the runner caused the ball to be dislodged. Judgement call on the umpire.