Plugin crashes after a short period of time

[TechCanuck]

The following output is seen in logs

  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluentd-1.6.2/lib/fluent/event.rb:107:in `each'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluent-plugin-retag-0.1.1/lib/fluent/plugin/out_retag.rb:72:in `process'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluentd-1.6.2/lib/fluent/plugin/output.rb:785:in `emit_sync'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluentd-1.6.2/lib/fluent/event_router.rb:96:in `emit_stream'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluentd-1.6.2/lib/fluent/event_router.rb:87:in `emit'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluent-plugin-retag-0.1.1/lib/fluent/plugin/out_retag.rb:73:in `block in process'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluentd-1.6.2/lib/fluent/event.rb:107:in `each'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluent-plugin-retag-0.1.1/lib/fluent/plugin/out_retag.rb:72:in `process'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluentd-1.6.2/lib/fluent/plugin/output.rb:785:in `emit_sync'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluentd-1.6.2/lib/fluent/event_router.rb:96:in `emit_stream'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluentd-1.6.2/lib/fluent/event_router.rb:87:in `emit'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluent-plugin-retag-0.1.1/lib/fluent/plugin/out_retag.rb:73:in `block in process'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluentd-1.6.2/lib/fluent/event.rb:107:in `each'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluent-plugin-retag-0.1.1/lib/fluent/plugin/out_retag.rb:72:in `process'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluentd-1.6.2/lib/fluent/plugin/output.rb:785:in `emit_sync'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluentd-1.6.2/lib/fluent/event_router.rb:96:in `emit_stream'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluentd-1.6.2/lib/fluent/event_router.rb:87:in `emit'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluent-plugin-retag-0.1.1/lib/fluent/plugin/out_retag.rb:73:in `block in process'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluentd-1.6.2/lib/fluent/event.rb:107:in `each'
  2019-07-25 16:39:05 +0000 [error]: #0 /usr/lib/ruby/gems/2.5.0/gems/fluent-plugin-retag-0.1.1/lib/fluent/plugin/out_retag.rb:72:in `process'

using the config

<match **-service**>
  @type retag
  add_prefix s4_
</match>
<filter com_**>
  @type parser
  key_name log
  reserve_data true
  remove_key_name_field true
  <parse>
    @type json
  </parse>
</filter>
<match fluent.**>
  @type retag
  tag clear
</match>