I spawned two Slammer, take gunner if first and shot at second one. There is clearly audible glitch which seems to be apper when two sounds with the same characteristics are played at the same time.
If shoot terrain objects or the ground, apparently there is no glitches
check this video → https://youtu.be/eUyZdX5aJLE
For video I modify arma for remove tank shot sounds to make more clarity explosion sound issue, modified with next code (for slammer)

cpp
class Mode_SemiAuto;
class CfgWeapons
{
	class CannonCore;
	class cannon_120mm: CannonCore
	{
		class player: Mode_SemiAuto
		{
			class StandardSound
			{
				SoundSetShot[]=
				{
					""
				};
			};
		};
	};
};