Sound wave in a sound cue (gunshot) randomly doesn't play from time to time

Hi,
I have a rather standard sound cue for a gunshot with a few randomized layer groups playing at the same time when a gun is fired. Worked ok until now when it sometimes won’t play a wave but only from one and the same group. Other layers are played. I’m not aware of anything I’ve done that would cause this. I dug into concurrency but it seems this isn’t the issue as not so many sounds are playing at any one time. Any suggestions please? Thanks so much for any help!

I’m adding a screenshot. The modulator isn’t causing it (volume from 0.9 to 1.05), the random node has weights all set to 1. I haven’t changed anything in this sound cue in a long time and suddenly it started happening.

EDIT: I tried to connect smaller chunks to the output and the whole ‘Crossfade by Distance part’ on the top works fine when going to the output. But when I add it to the final mixer with the two lower parts it starts happening. It doesn’t make sense. The mixer is set up with volumes 1, 0.2, 1. Looks like a bug to me.

EDIT2: The culprit is the first input of the last mixer. The last mixer’s second and third input is ok. Randomly won’t play the first input.