The usage of @Store violates the synchronised access to shared mutable data with MicroStream principle. See also https://docs.microstream.one/manual/storage/root-instances.html#_synchronize_access_to_shared_mutable_data

When a call to StorageManager.store() is not protected with the same lock or synchronised on the same 'Object' then the change that is made to the Object graph, a ConcurrentModificationException modification exception can be thrown when using a collection (List, Set, ...). This is because the MicroStream internals are inspecting the structure and it is modified at the same time by the user code.