Ghost notifications?

I have an iPhone 12 Pro Max (even though you can't select it as the device when asking a question on this forum) and an Apple Watch 6 - 44mm. If I place my iPhone on it's wireless charging stand in the morning for work, 90% of text messages or WhatsApp notifications do NOT light up the screen, make a noise or buzz (on ring or silent, respectively), and no ping on my Apple Watch either. This is infuriatingly reproducible. I lift or tap the screen to wake, and there could be 12 messages that never announced themselves!

After consultation with Apple support, the last troubleshooting item they suggested is upsetting: restore as a new phone and live with it for a day or two to see if I can reproduce the issue (because they think there may be corruption in the iPhone backup I restored it from).

I came from iPhone 11 Pro Max, never had this issue with it. That was restored from a backup from the phone before it and so on. At least back to iPhone 6s, I believe, my iCloud backups have been restored to each new phone.

Before I live with my phone as a fresh install and see if I can reproduce it – which if I can, I will be utterly devastated because I believe there will be no fix – has anyone else experienced this and found the cause?

Before anyone asks, Do Not Disturb is NOT on, the Apple Watch is set to mirror my iPhone and unlocked when on wrist, and notifications from Messages and WhatsApp are always allowed, and none of the contacts have had their messages muted.

Thanks for listening to my rant. Now over to asking another question about HomeKit which is not acting as it should. And I've had three calls for over an hour each with a senior expert who can't resolve it. Does Apple pay for "glitch bounties," because I have more...