Support for APM Agent central config was added to the integration in 7.14.0, so you should not be seeing those errors. Are you running 7.14.x?
Running 7.14.2 across the board. It seems the errors are due to the Beats Agents and their APM Instrumentation, as this is the offending query captured below, communicating with the Fleet's Elastic Agents APM Service's response. In this case it for Auditbeat
# Instrumentation support for the packetbeat.
# Set to true to enable instrumentation of packetbeat.
# Environment in which packetbeat is running on (eg: staging, production, etc.)
# APM Server hosts to report instrumentation results to.
# API Key for the APM Server(s).
# If api_key is set then secret_token will be ignored.
# Secret token for the APM Server(s).
There is not problem with the data getting into the APM Kibana dashboards, it just seems the Beat Agents are trying to get a configuration of sorts. 192.168.0.7 (GaalDornick)