My iphone ringer sometimes not working. Specially MSGs, Music, Videos

Try to reset the phone by holding the sleep and home button for about 10sec, until the Apple logo comes back again. You will not lose data by resetting.

If this does not work, set it up as new device again:

Use iTunes to restore your iOS device to factory settings - Apple Support

If still no luck, get it checked by visiting an Authorized Apple Service Provider, Apple Store, or contact Apple Support:

iPhone - Contact Support - Apple Support

You're welcome, glad it's working again 🙂

Did you try to set it back to factory settings without using the backup, in case it contains corrupt data?

If the sound is delayed, this must be software related.

To rule that out, set it back to factory settings, without using any backup data afterwards. Set up the rest of the personal settings manually and test the phone.

If it still does not work, then this is a hardware issue and the phone has to be serviced by Apple or an Authorized Apple Service Provider:

Use iTunes to restore your iOS device to factory settings - Apple Support

Find an Apple Authorized Service Provider

iPhone - Contact Support - Apple Support