Per <SG6> and as made clear in this Q&A, a referee may clear a stuck fully scored ball. However, our team participated in a match recently where a referee standing next to the goals during a Final match refused to do so when implored to do so by the drive team. The stuck ball impeded the teams' ability to score further in the match. The ball was fully scored, and another ball was partially scored and stuck.
Another similar situation is in <SG4>: "If a Ball is introduced improperly outside of the Loading Station...the Ball must be retrieved by a referee and handed to a Loader."
In both cases, nothing in the manual obligates the referee to perform these duties in a timely manner. In the second case, one might view that as a "penalty" for incorrectly loading. But in the first scenario, usually stuck balls are outside of the control of the drive team.
May the Loader in these cases also perform these duties? For example, a ball is stuck and the loader unsticks it. Or a referee calls out an improper load, and the loader retrieves and re-loads the ball. This would decrease the burden on the referees, who may be on the opposite end of the field for example, and have to run around to clear a stuck ball (or may choose to walk very very slowly).