I haven’t modified the file, I deleted it and it gets re-created every time. The system doesn’t use a sd card but a ssd which is healthy. 
Can you have a look at that character in the file? And replace it maybe? Before putting it back from the UI?
I tried using sublime text and reaching character 86216 i see a letter “a”. I higlighted it with **a**
{
"aliases": [],
"area_id": null,
"capabilities": null,
"config_entry_id": null,
"device_cl**a**ss": null,
"device_id": null,
"disabled_by": null,
"entity_category": null,
"entity_id": "automation.laundryroom_ventilation_timer",
"hidden_by": null,
"icon": null,
"id": "787f67d30d76466bf6a80ebdde706915",
"has_entity_name": false,
"name": null,
"options": {},
"original_device_class": null,
"original_icon": null,
"original_name": "Laundryroom ventilation timer",
"platform": "automation",
"supported_features": 0,
"translation_key": null,
"unique_id": "cf063a3a5d984cb7a3bc85d225b0a5b1",
"unit_of_measurement": null
},
That’s probably not the right place, as device_class is a valid tag.
That will be really annoying to debug.
Maybe an online json validator, can you copy paste your whole file there?
And press “Validate JSON”
It’s a valid JSON according to that validator.
Try the provided solution on that file (.storage/core.entity_registry) and let us know.
iconv -f iso-8859-1 -t utf-8 .storage/core.entity_registry > .storage/core.entity_registry.converted
and compare the 2 files if you can (or just replace one with the other)
2 Likes
Thank you so much! This solved my problem 
EDIT: nope, on the second restart the problem reappears
1 Like
Damn, you should do a comparison then, it means that something from your config is recreating the error.
It will guide you to the integration/entity that is culprit
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So the question is why home-assistant is creating a version of the file with the wrong encoding?
Upon pening the file with kedit, I receive the following error:
The file you opened has some invalid characters. If you continue editing this file, you could corrupt this document.
You can also choose another character encoding and try again.
The content of the file core.entity_registry and core.device_registry is coming from the configuration.yaml + all the integrations + all customizations + …
If you put an iso-8859-1 encoded character (by saving with a windows application for exemple) in one of the files used by HA to recreate the core files, when the file will be re-created, it will contain that character and the whole process will fail.
I know that because I did a modification in HA that included a french character that HA did not like. I knew which one it was and replaced it with another more “English friendly” one.
EDIT: Doing a diff between the files will pinpoint the character that HA doesn’t like in that file and will most probably help you modify another file such as at the next restart, the core file will not include it again.
I found the culprit! Look at the last line, there is a question mark instead of °.
This is that this is a zwave sensor, how can I debug the problem from now? It never created this issue in older versions of HA.
{
"aliases": [],
"area_id": null,
"capabilities": {
"state_class": "measurement"
},
"config_entry_id": "645f5c225c839ffac1d4fa6d81c15fd5",
"device_class": null,
"device_id": "0b6af9320e8b4a1aaf8fc5a447fb4c2f",
"disabled_by": null,
"entity_category": null,
"entity_id": "sensor.living_room_temperature",
"hidden_by": null,
"icon": null,
"id": "9e3e59afe0ed0dd28805cdd796af3639",
"has_entity_name": false,
"name": null,
"options": {},
"original_device_class": "temperature",
"original_icon": null,
"original_name": "Living Room Temperature",
"platform": "esphome",
"supported_features": 0,
"translation_key": null,
"unique_id": "esp01sensorliving_room_temperature",
"unit_of_measurement": "?C"
},
I was about to mention that this
Is the degree symbol.
Have a look at the configuration of that sensor in ESPHome.
1 Like
Said it in reply #1 
2 Likes
You should have a yaml file describing your sensor in ESPHome, lsomething that look like this:
esphome:
name: DaikinAP36230
platform: ESP32
board: mhetesp32devkit
wifi:
ssid: !secret wifi_ssid
password: !secret wifi_password
web_server:
port: 80
auth:
username: admin
password: !secret web_server_password
logger:
api:
ota:
esp32_ble_tracker:
Also in that ESPHome file it is this specific sensor: Living Room Temperature
It is not an esp01, it is an AC by daikin so there’s no settings to modify.
I don’t know about that Daikin AC integration.
Maybe it should be adapted for the latest release of HA.
You can always open a ticket for that.
In the mean time, either go back to previous version of HA or disable the Daikin AC integration.
Unless someone else has a better idea?