Kafka connect schema registry timeout

I am running a kafka JDBC sink connector with the following properties:

{
    "connector.class": "io.confluent.connect.jdbc.JdbcSinkConnector",
    "table.name.format": "events",
    "connection.password": "******",
    "tasks.max": "1",
    "topics": "events",
    "value.converter.schema.registry.url": "http://IP:PORT",
    "db.buffer.size": "8000000",
    "connection.user": "postgres",
    "name": "cp-sink-events",
    "value.converter": "io.confluent.connect.avro.AvroConverter",
    "connection.url": "jdbc:postgresql://IP:PORT/postgres?stringtype=unspecified",
    "insert.mode": "upsert",
    "pk.mode": "record_value",
    "pk.fields": "source,timestamp,event,event_type,value"
}

It was working fine before, but since this week I have been getting the following errors while trying to sink my data to Postgres:

Caused by: org.apache.kafka.common.errors.SerializationException: Error retrieving Avro value schema for id 4
Caused by: java.net.SocketTimeoutException: connect timed out

It appears my kafka connect cannot acces my schema registry server anymore. I coulnd't manage to figure out why or how. I have tried multiple things but yet to find the solution. I did install NGINX on this VM over last week, and killed apache2 which was running on port 80. But I haven't found any dependencies that this would cause any problems.

When I visit my schema registry URL by hand it works fine (http://IP:PORT/schemas/ids/4). any clue how to proceed?

confluentinc / kafka-connect-jdbc

Kafka connect schema registry timeout #1295