I have the same problem (which supposedly does not happen to all users of that extension). I fix it by running this script once a month (it deletes the temporary containers from the containers.json file):

    import json

    with open('containers.json.bac') as f:
        s = f.read()
        j = json.loads(s)
        ids = [i for i in j['identities'] if not i['name'].startswith('tmp')]
        print(len(j['identities']), len(ids))
        j['identities'] = ids
        with open('containers.json', 'w') as wf:
            wf.write(json.dumps(j))