iPhone lock sound linked to media volume instead of ringer volume.

Update: An alternative fix has been found (published as a comment on my YouTube video).

Rather than deleting your bank card(s) from your Apple Pay wallet, go to Settings > Wallet & Apple Pay, then turn off 'Double-Click Side Button'. That should resolve the sound issue. You won't be able to launch wallet with a double-click anymore, however, Apple Pay should still launch automatically when you bring your phone near a contactless reader.

If you have this lock click volume issue, please take a moment to report the bug to Apple using the link below. They won't fix it if they don't know about it. https://www.apple.com/feedback/iphone.html

HOLY S%$T! Looks like that's it! I added a credit card to my Apple Pay wallet a while ago, but wasn't able to correlate the issue to Apple pay as I only added a card after jumping to a new phone.

I just deleted my card from my Apple Pay wallet (I only had one card entered) and the issue was immediately gone. Volume of the lock sound is no longer tied to the volume bar in the control centre, and is now tied to the volume of ringer again. I didn't even have to restart the phone.

Thank you very much for making your post, it's been very helpful as I'm pretty sure we've nail down the issue! I'll add my card back again and see whether the issue returns to try and confirm.

So to troubleshoot this issue I put my phone into DFU mode then did a full software restore with iOS 13.1.3. At first the issues was resolved, but after a short while (hour or so) the lock sound had reverted back to being linked to the media volume, rather than the ringer volume.

Going to take it into an Apple store I think, to see what one of the geniuses have to say. Sigh.

The lock click volume being tied to the media volume is definitely not normal behaviour. Here's a video comparing behaviour of a '7 Plus' and 'X', which don't have the fault, versus my 'Xs Max', which has the fault.

The order in which the phones are demo'd are 7 Plus, then X, then Xs Max.

https://youtu.be/PKH5sswzfus

FIX CONFIRMED!

I added my bank card back into my wallet and the problem immediately returned. I deleted it again, gone. I then added a different bank card to my Apple Pay wallet and the problem immediately came back, which indicates that the issue is not specific to a particular bank card.

So, this one appears to be solved, at least in terms of understanding what's causing the sound issue, and we now need to get this on Apple's radar so they develop a permeant fix. Now that I've had to delete my card from my wallet, I'll have to revert to actually carrying a physical wallet :(

I just installed iOS 13.3 and can confirm that the Apple Pay lock sound bug in NOT fixed, unfortunately.

Additionally, for those who have disabled 'double click side button' within Apple Pay, to prevent the sound issue, be aware that 'double click side button' automatically re-enables during the install of iOS 13.3. So, you'll need to go back and disable it again.

Please keep submitting to feedback to Apple on this issue using 'Feedback Assistant.app' (do a Spotlight search).

The plot thickens.

I've been reading other posts where people have found that disabling Siri alleviates similar volume issues related to notifications. So I set up my Xs Max (iOS 13.3) so that the sound issue was occurring (ie bank card added to my Wallter and 'double-click side button' enabled within Wallet & Apple Pay) and I tried disabling 'Press side Button for Siri'. The lock sound bug was immediately alleviated. So something is definitely wrong with the way the side button is currently setup/programmed.

Another thing: I just noticed that my lock click volume bug does not occur when my phone is connected to my bluetooth headphones. Just throwing that info in on the off chance that an Apple engineer comes reading through this thread.

"So you mean if I add a bank card, then disable side-button Siri, the lock sound volume bug would be gone?"

yes, it should be. That's how it was working for me, even with 'Double-Click Side Button' enabled in Wallet & Apple Pay.

I'm keeping Siri enabled as I use it, but am keeping Double-click side button disabled for Apple Pay, as Wallet automatically launches once you bring your phone near a contactless payment terminal anyway.