Which condition may indicate that the locking block of the M9 pistol is damaged?

The condition indicating that the locking block of the M9 pistol may be damaged is when the barrel does not return to battery. The locking block plays a crucial role in the operation of the pistol by ensuring that the barrel and the slide move together during the firing cycle. If the locking block is compromised, it can prevent the barrel from properly locking into position after firing, which is referred to as not returning to battery. This condition can lead to malfunctioning of the firearm, as the barrel needs to be fully seated to ensure that the next round can be chambered safely and the firearm can function properly.

In contrast, while spongy trigger feedback, slide resistance, and issues with magazine ejection could indicate other issues with the firearm, they do not specifically point to a problem with the locking block itself. The function of the locking block directly correlates with the barrel's ability to return to battery, making this condition a clear indicator of potential damage.