I have the following test that fails consistently:

using var realm = Realm.GetInstance(config);

var session = realm.SyncSession;
await session.WaitForUploadAsync();

// Removing the Stop() call here fixes the issue
session.Stop(); // calls SyncSession::pause()

realm.Dispose();

// Even adding a delay doesn't help here
Realm.DeleteRealm(config);

The error being thrown is Cannot delete files of an open Realm. I haven't been able to pinpoint the issue, but what I'm seeing is:

1. We call SyncSession::pause() which in turn calls SyncSession::do_become_inactive.
2. When we get to m_sync_manager->unregister_session, we get into auto existing_session = it->second->existing_external_reference(), which unlocks the lock, but doesn't remove the session from the map because someone is holding a reference to the session (this is the SDK).
3. When the SDK calls realm.Dispose that also closes the managed session, which goes into SyncSession::ExternalReference::~ExternalReference.
4. SyncSession::did_drop_external_reference calls SyncSession::close, but because we're in Paused state, we unlock the state mutex without unregistering the session from the sync manager.

I'm not sure if the sync client does anything special about paused sessions, but it doesn't appear like it's closing the Realm, which then prevents the deletion.