When editing non-main-language content in the admin a ContextErrorException error is triggered. This only happens if the content in question has an object relation field type as a part of the content type.

Notice: Undefined property: eZContentObjectAttribute::$languageCode

This appears to happen on eZObjectRelationType::storeObjectAttribute because the eZContentObjectAttribute is not accessed correctly correctly. The case is wrong on the accessor (languageCode vs LanguageCode). Rather than fixing the case though, the attribute() function should be used to access the language code.

$existingRelations[$attributeTranslation->attribute('language_code')] = (int)$attributeTranslation->attribute( 'data_int' );