Audio action "play at object" make sound cracking on mobile spekers??

Hi, I just got a discussion topic. Today I tested my game via my phone (iPhone 6+) and strangely found that when I hit an enemy and make it plays a hurt sound using Play at object, all of the sounds randomly start cracking and it was even worst for the next upcoming sounds.

I also tried to analyze if a cloth moving or high-pitch sound overlapping with a low-frequency sound and audio with timescale caused this, but no. I figure out that using Play at position(Enemy.x, Enemy.Y) instead of Play at object solves this problem.

I'm not sure if this is a bug or I don't know well about those two audio functions.

"I tested on chrome & safari browser"

"Enemy that I said is not a single sprite object, it is a family object type."

Edit: I found that it's not about the audio action, and sorry for my misunderstanding here it's actually randomly happened only to my old iphone.