Kafka_ex :unsupported_version

On our staging server we have Kafka 2.8.1 installed. Running our app with kafka_ex 0.13 gives a :unsupported_version error: (our app is called dockr, not a typo )

 | 10:00:39.308 [error] GenServer #PID<0.1259.0> terminating
app_1  | ** (CaseClauseError) no case clause matching: :unsupported_version
app_1  |     (kafka_ex 0.13.0) lib/kafka_ex/gen_consumer.ex:929: KafkaEx.GenConsumer.load_offsets/1
app_1  |     (kafka_ex 0.13.0) lib/kafka_ex/gen_consumer.ex:660: KafkaEx.GenConsumer.handle_info/2
app_1  |     (stdlib 4.2) gen_server.erl:1123: :gen_server.try_dispatch/4
app_1  |     (stdlib 4.2) gen_server.erl:1200: :gen_server.handle_msg/6
app_1  |     (stdlib 4.2) proc_lib.erl:240: :proc_lib.init_p_do_apply/3
app_1  | Last message: :timeout
app_1  | State: %KafkaEx.GenConsumer.State{consumer_module: Dockr.Kafka.Consumer, consumer_state: nil, commit_interval: 1000, commit_threshold: 100, worker_name: #PID<0.1260.0>, group: "dockr-cg", topic: "dockr", partition: 1, member_id: "kafka_ex-8066c9fb-9d7b-40e9-8159-91e06eec48d0", generation_id: 17, current_offset: nil, committed_offset: nil, acked_offset: nil, last_commit: nil, auto_offset_reset: :earliest, fetch_options: [auto_commit: false, worker_name: #PID<0.1260.0>], api_versions: %{fetch: 0, offset_commit: 0, offset_fetch: 0}}

I have tried to reproduce the issue locally; I can not find a kafka docker container or an install that has 2.8.1;
I tried it wih with all kinds of versions of cp-confluent (6.2.x), also installed kafka 2.8.2 from apache, but it all works well locally.

Anyone recognizes this what could be the issue?

Many thx in advance.