Correctable Error appeal/Stop play during a live ball?

[BayStateRef]

A1 takes a shot from beyond the 3-point line that goes in. Neither official indicates it is a 3-point basket.

As B is starting a fast break after retrieving the ball, Team A coach goes to the table to ask for a time out for a correctable error under Rule 5-8-4.

Is the timer supposed to wait for a dead ball or team control by Team A to sound the horn...or must the timer sound the horn immediately...even if it is during the fast break? And as the official, must you recognize the horn immediately and blow the whistle? If Team B scores and the ball is inbounded, it is too late to correct the error, since that would be the second live ball following the error.

Case book plays for 5.8.4 seem to suggest the timer should sound the horn immediately and the official should stop play with a whistle.