It looks like you upgraded from
3.13.0 which didn't have our Spymemcached instrumentation to a newer version that does.
One thing you can try is disabling that instrumentation package altogether. If you'd like to give that a try, you can update your
newrelic.yml with the following:
That will disable the Spymemcached instrumentation and the related messages should disappear from your logs. All other instrumentation packages will be unaffected.