Live activity sometimes won't update or create

**iOS device model, version and app version**

Model Name: iPhone 17
Software Version: 26.6
App version: 2026.8.0 (2026.2739) via TestFlight

**Home Assistant Core Version**

2026.8.1

**Describe the bug**

The live activity can sometimes :
- work properly
- be created and updated, then stopped updating (in that case when I dismiss the live activity, it can be recreated)
- not be created at all

I have only one automation which uses a live activity : for showing my EV charging progress.

The live activity isn't refreshed very frequently : from 5 to 25 min (minimum 5 min because of the Renault integration fetch, maximum 25 min for a battery percentage increase on a 8A slow charge intensity).

The backend is sending the live notification BUT, it is not showing on my iPhone.

**To Reproduce**
I don't know.
With the exact same automation: sometimes the live activity will work as expected, sometimes it creates updates few times, then stop updating, or even sometimes it won't create at all.

**Expected behavior**
Create and update the live activity when sent by the backend.

**Screenshots**

https://github.com/user-attachments/assets/09a1be11-a422-4cdb-8967-b64314e56c33

**Additional context**

No source files, tests, or entry points are identified. Start by reproducing the EV-charging automation with the reported iOS and app versions, then trace how backend live notifications are received and applied to the Live Activity. Done means explaining and fixing the intermittent creation or update failure, with coverage for the relevant behavior.

Written by the indexing model from the issue text.