[ERROR][logstash.instrument.periodicpoller.jvm] Periodi cPoller: exception

The reason the CSV parsing stops after the m6 column is the newline character. This is a known bug (below). You're using Filebeat to collect the logs, right? If so you might be able to work around the bug by moving the multiline processing to Filebeat. You should do that anyway since it'll be more reliable, but if it also solves this problem then all the better.