iPhone inconsistent vibration in ring mode when locked

Hello,

I am experiencing an issue with vibration (haptics) on my iPhone 15 Pro Max.

The behavior is inconsistent:

• The phone vibrates normally when it is unlocked.
• It also vibrates when set to silent mode.
• However, when the phone is locked and in ring mode, it often does NOT vibrate for notifications, even though notification sounds are working.

Sometimes the vibration works temporarily (for example after changing settings or restarting the device), but then it stops again without any clear reason.

I have already tried:

• Enabling “Play Haptics in Ring Mode” and “Play Haptics in Silent Mode”
• Toggling “System Haptics” off and on
• Restarting the device
• Checking Focus modes (Do Not Disturb is off)
• Verifying that vibration is enabled in Accessibility settings

This leads me to believe it may be a software-related issue rather than a hardware problem, since vibration works in some scenarios.

Could you please advise on a solution?

Thank you.

[Re-Titled by Moderator]

Original Title: Problem with Haptics