Error message - Unexpected character encountered while parsing value: <. Path '', line 0, position 0

Hi there,
in my setup, I am running Agent DVR and Deepstack together as docker containers. I had them setup and configured, as I found from corresponding ressources.

In the logfile in Agent DVR I get the following error:

16:25:18	DeepStack Alert Filter: DeepStack Alert Filter: Unexpected character encountered while parsing value: <. Path '', line 0, position 0.
16:25:18	Error: DeepStack Alert Filter: DeepStack Alert Filter: Unexpected character encountered while parsing value: <. Path '', line 0, position 0.
16:25:18	DeepStack Alert Filter: at Newtonsoft.Json.JsonTextReader.ParseValue() at Newtonsoft.Json.JsonReader.ReadForType(JsonContract contract, Boolean hasConverter) at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent) at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType) at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings) at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings) at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value) at CoreLogic.AI.AlertFilter.Detect(Byte[] jpeg, List`1 regions, Size sz)
16:25:18	Error: DeepStack Alert Filter: at Newtonsoft.Json.JsonTextReader.ParseValue() at Newtonsoft.Json.JsonReader.ReadForType(JsonContract contract, Boolean hasConverter) at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent) at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType) at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings) at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings) at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value) at CoreLogic.AI.AlertFilter.Detect(Byte[] jpeg, List`1 regions, Size sz)
16:25:18	Unexpected character encountered while parsing value: <. Path '', line 0, position 0.
16:25:18	Will retry AI processing in 30 seconds.

The motion detection of the system works.

As far as I understand it, this error prevents Agent DVR to record a detected motion, as it is setup to do that only, if there is a response from deepstack. Otherwise the recording will not be executed.

What should I check to get rid of the error message?

Thanks a lot!

Edit: sorry, forgot to mention the version: DeepStack: Version 2022.01.01