ERROR Consumer read callback threw an unhandled exception

Clients REST Proxy
1

Hello!
I use confluentinc/cp-kafka-rest:8.0.0 docker container.
Every time when I try to get messages
GET /consumers/testgroup/instances/my_consumer/records
I see error

ERROR Consumer read callback threw an unhandled exception
id=io.confluent.kafkarest.v2.KafkaConsumerReadTask@792122b5
exception=null (io.confluent.kafkarest.v2.KafkaConsumerReadTask)

When I try consume 2 or 4 times I get messages.
I can’t understand why this error occurs.

Create and subscribe without errors.