Class xx was not found in the chain configured namespaces - symfony

Question

I have two databases for my application so I put the entities in two separate folders to simplify things.
Entity/
Local/
User.php
Foo.php
Remote/
Bar.php
but I have an error 500 that I don't understand at the time of connection
[2020-09-03 17:10:58] request.CRITICAL:
Uncaught PHP Exception Doctrine\Persistence\Mapping\MappingException: "The class 'App\Entity\Local\User' was not found in the chain configured namespaces " at /www/myapp/vendor/doctrine/persistence/lib/Doctrine/Persistence/Mapping/MappingException.php line 23 {"exception":"[object] (Doctrine\\Persistence\\Mapping\\MappingException(code: 0): The class 'App\\Entity\\Local\\User' was not found in the chain configured namespaces at /www/myapp/vendor/doctrine/persistence/lib/Doctrine/Persistence/Mapping/MappingException.php:23)"} []
Here is my doctrine.yml configuration
doctrine:
dbal:
default_connection: local
connections:
local:
url: '%env(resolve:DATABASE_URL)%'
driver: 'pdo_mysql'
server_version: '5.7'
charset: utf8mb4
remote:
url: '%env(resolve:DATABASE_URL_MS)%'
charset: 'UTF-8'
wrapper_class: App\Connections\ConnectionRemote
mapping_types:
timestamp: string
xml: string
schema_filter: $sales$
orm:
auto_generate_proxy_classes: '%kernel.debug%'
default_entity_manager: local
entity_managers:
local:
connection: local
mappings:
local:
is_bundle: false
type: annotation
dir: '%kernel.project_dir%/src/Entity/Local'
prefix: 'App\Entity\Local'
alias: local
AnotherBundle: ~
remote:
connection: remote
mappings:
remote:
is_bundle: false
type: annotation
dir: '%kernel.project_dir%/src/Entity/Remote'
prefix: 'App\Entity\Remote'
alias: remote
Even stranger, if I refresh my page, I am well connected and the error doesn't come back...
Even crazier, it works very well in dev mode

Answer 1

I think there's a bug in Doctrine, it's the fact that it works in dev and not in prod that put me on the track of the solution.
I had dumped the dev and prod conf to compare the two versions and what I noticed was that doctrine.orm.default_entity_manager was set to default even though it is set to custom in package/doctrine.yaml.
so for the value to be really taken into account you must also set doctrine.orm.default_entity_manager in prod/doctrine.yaml
doctrine:
orm:
default_entity_manager: local