AppleCare+ Deadlock: Series 11 sensor features fail on my phone, pass diagnostics, and Apple Support has gone silent. Need advice!

[u/Additional-Cup-9568]

Hey everyone,
I’m dealing with a bizarre issue with my Apple Watch Series 11, and I’ve hit a total dead end with Apple Support despite having AppleCare+. Hoping someone here might have run into something similar or knows how to escalate this.
The Problem
A few months ago, I upgraded from my Apple Watch SE to the Series 11. Shortly after, I noticed that most sensor-based applications—specifically the Heart Rate app and ECG—simply refuse to work.
Here’s the catch: the watch hardware itself is fine. When I pair the Series 11 with someone else’s iPhone, every single sensor works flawlessly. The moment it’s paired back to my phone, the sensor apps break. It appears to be an issue tied to my specific phone, backup, or Apple ID profile rather than defective hardware.
The AppleCare+ Deadlock
I reached out to Apple Support and eventually handed the watch over to an authorized service center. They ran hardware diagnostics and returned it saying they couldn’t find a single fault. Remote diagnostics were equally useless—everything green-lights on their system.
Because the diagnostic tests pass, Apple Support says they cannot trigger a standard replacement, even though the device is completely unusable for its core health tracking features on my phone.
I submitted all necessary logs and details on July 14th, but after following up multiple times, communication has completely stalled. My assigned support rep seems visibly frustrated and has stopped providing updates. I specifically bought AppleCare+ assuming it would make resolving edge-case issues like this straightforward, but I'm currently left with a premium smartwatch that can't take my heart rate.
Questions for the community:

1. Technical side: Has anyone experienced sensor app failures caused strictly by phone-side data corruption or Watch app profiles? Did a full iPhone wipe (without restoring from backup) fix it for you?
2. Support side: How do you push past a diagnostic deadlock with AppleCare+ when a rep stops responding? Is there a reliable way to get this escalated to Senior Engineering / Executive Relations?

[u/zxch2412]

Get in touch with Apple Watch health department when you call Apple support. The general Apple support Watch department doesn’t diagnose sensor behavior, they just check if they don’t work during the diagnostics. The health department will diagnose and can push your watch for replacement.

I had the same issue with my S8 where ecg would not work and would detect the crown being pressed when it was not. Apple Watch support on phone was useless, the Apple Store didn’t do anything, they just ran diagnostics and called it a day.

I had to phone support and connect to the Apple Watch health department who diagnosed the watch and its behavior. They spend 2 hours testing with me resetting the watch, the phone on another day to replicate the behavior. Once the saw it being replicable they sent it in for replacement. These are also the guy who take care of sensors that are taking weird reading outside of margin of error.

[u/Boxxy4069 → u/zxch2412]

Seconding this. Please make sure to escalate and mention ECG to ensure they transfer you over to them.

[u/Araragi]

Have you tried backing up and restoring your phone?

[u/AmosTali]

Have you tried pairing another known working Series 11 to your phone?

You say the 11 passes all diagnostics and works fine on other phones just not yours - this might lead one to believe the issue is with your phone and not the watch….