Sometimes, attempting to run lambdas will return this type of error:
```
{"Type": "Server", "message": "Error executing Lambda function arn:aws:lambda:ap-northeast-1:000000000000:function:service-stage-functionName: An error occurred (ResourceAlreadyExistsException) when calling the CreateLogGroup operation: The specified log group already exists Traceback (most recent call last):\n 
File \"/opt/code/localstack/localstack/services/awslambda/lambda_api.py\", line 338, in run_lambda\n 
event, context=context, version=version, asynchronous=asynchronous)\n 
File \"/opt/code/localstack/localstack/services/awslambda/lambda_executors.py\", line 81, in execute\n 
return do_execute()\n File \"/opt/code/localstack/localstack/services/awslambda/lambda_executors.py\", line 70, in do_execute\n self._store_logs(func_details, log_output, invocation_time)\n 
File \"/opt/code/localstack/localstack/services/awslambda/lambda_executors.py\", line 105, in _store_logs\n logs_client.create_log_group(logGroupName=log_group_name)\n 
File \"/opt/code/localstack/.venv/lib/python3.6/site-packages/botocore/client.py\", line 357, in _api_call\n 
return self._make_api_call(operation_name, kwargs)\n 
File \"/opt/code/localstack/.venv/lib/python3.6/site-packages/botocore/client.py\", line 661, in _make_api_call\n 
raise error_class(parsed_response, operation_name)\n
botocore.errorfactory.ResourceAlreadyExistsException: An error occurred (ResourceAlreadyExistsException) when calling the CreateLogGroup operation: The specified log group already exists\n", "__type": "InternalFailure"}
```
I am not yet sure if there are any particular settings that cause it, since it does not occur for certain deployments.

Will update if I can figure out the exact configuration.
event_file = EVENT_FILE_PATTERN.replace('*', short_uid())
        save_file(event_file, json.dumps(event))
        TMP_FILES.append(event_file)
        class_name = handler.split('::')[0]
        classpath = '%s:%s' % (LAMBDA_EXECUTOR_JAR, main_file)
        cmd = 'java -cp %s %s %s %s' % (classpath, LAMBDA_EXECUTOR_CLASS, class_name, event_file)
        result, log_output = self.run_lambda_executor(cmd)
        LOG.debug('Lambda result / log output:\n%s\n> %s' % (
            result.strip(), log_output.strip().replace('\n', '\n> ')))
        return result, log_output
class Util:
    debug_java_port = False
    @classmethod
    def get_java_opts(cls):
        opts = config.LAMBDA_JAVA_OPTS or ''
        if '_debug_port_' in opts:
            if not cls.debug_java_port:
                cls.debug_java_port = get_free_tcp_port()
            opts = opts.replace('_debug_port_', ('%s' % cls.debug_java_port))
        return opts
EXECUTOR_LOCAL = LambdaExecutorLocal()
EXECUTOR_CONTAINERS_SEPARATE = LambdaExecutorSeparateContainers()
EXECUTOR_CONTAINERS_REUSE = LambdaExecutorReuseContainers()
DEFAULT_EXECUTOR = EXECUTOR_LOCAL
AVAILABLE_EXECUTORS = {
    'local': EXECUTOR_LOCAL,
    'docker': EXECUTOR_CONTAINERS_SEPARATE,
    'docker-reuse': EXECUTOR_CONTAINERS_REUSE
}