Chapter 16: The Rescue - S2-E8
Other mistake: The inexplicably omniscient Moff Gideon mentions that Mando fired his wrist launcher's "one and only salvo." This would confirm what could be assumed by the dialogue with the Armorer in episode 1.3: the Whistling Birds are rare, and made of Beskar. Mando uses them in 1.3 immediately, then he still has them in 1.6 to use them against Burg. He replenishes his ammo in the season finale so we can assume that includes the birds. In season 2 he uses them in 2.1 in the prologue and then in 2.6. Seems abnormal to say the least that he'd have still some to use in 2.8 with no more refills.