Unsure if it's the right way to suggest an addition, but here's how I made it work. At line 2024 (Version 4.2.0) I added:

			if(entity is SpookySpeaker spookySpeaker)
			{
				if (spookySpeaker.IsOn())
					spookySpeaker.InvokeRandomized(spookySpeaker.SendPlaySound, spookySpeaker.soundSpacing, spookySpeaker.soundSpacing, spookySpeaker.soundSpacingRand);
			}​

Thanks and have a nice day!