Lock sound disappears intermittently on iPhone when using the power button

sometimes while locking the phone using power button, lock sound totally disappears, it's interrupting a user experience, I confirmed from settings that lock sound is enabled though I'm facing such issue, I also restarted but no permanent solution .

I would like to address apple team to look into this matter, if it's a bug then there's an urge to fix it.

thank you, if any user is facing such please kindly address apple team

[Re-Titled by Moderator]

Original Title: lock sound issue