Here is an excerpt around the truncation (which happens at 11:27:17). I removed the actual events, to make it more readable.
It looks like the problem is a mismatch between the file size and the offset.
2018-04-04T11:27:09.831Z DEBUG [harvester] log/log.go:85 End of file reached: /data/logfiles/production_access.log; Backoff now.
2018-04-04T11:27:10.832Z DEBUG [logstash] logstash/async.go:142 2 events out of 2 events sent to logstash host logstash:5044. Continue sending
2018-04-04T11:27:11.230Z DEBUG [registrar] registrar/registrar.go:200 Processing 2 events
2018-04-04T11:27:11.230Z DEBUG [registrar] registrar/registrar.go:193 Registrar states cleaned up. Before: 1, After: 1
2018-04-04T11:27:11.230Z DEBUG [registrar] registrar/registrar.go:228 Write registry file: /usr/share/filebeat/data/registry
2018-04-04T11:27:11.313Z DEBUG [registrar] registrar/registrar.go:253 Registry file updated. 1 states written.
2018-04-04T11:27:11.699Z DEBUG [prospector] prospector/prospector.go:124 Run prospector
2018-04-04T11:27:11.699Z DEBUG [prospector] log/prospector.go:147 Start next scan
2018-04-04T11:27:11.701Z DEBUG [prospector] log/prospector.go:361 Check file for harvesting: /data/logfiles/production_access.log
2018-04-04T11:27:11.701Z DEBUG [prospector] log/prospector.go:447 Update existing file for harvesting: /data/logfiles/production_access.log, offset: 174437390
2018-04-04T11:27:11.701Z DEBUG [prospector] log/prospector.go:499 Harvester for file is still running: /data/logfiles/production_access.log
2018-04-04T11:27:11.701Z DEBUG [prospector] log/prospector.go:168 Prospector states cleaned up. Before: 1, After: 1
2018-04-04T11:27:11.834Z DEBUG [harvester] log/log.go:85 End of file reached: /data/logfiles/production_access.log; Backoff now.
2018-04-04T11:27:12.836Z DEBUG [logstash] logstash/async.go:142 3 events out of 3 events sent to logstash host logstash:5044. Continue sending
2018-04-04T11:27:12.886Z DEBUG [registrar] registrar/registrar.go:200 Processing 3 events
2018-04-04T11:27:12.886Z DEBUG [registrar] registrar/registrar.go:193 Registrar states cleaned up. Before: 1, After: 1
2018-04-04T11:27:12.886Z DEBUG [registrar] registrar/registrar.go:228 Write registry file: /usr/share/filebeat/data/registry
2018-04-04T11:27:12.951Z DEBUG [registrar] registrar/registrar.go:253 Registry file updated. 1 states written.
2018-04-04T11:27:13.838Z DEBUG [harvester] log/log.go:85 End of file reached: /data/logfiles/production_access.log; Backoff now.
2018-04-04T11:27:14.840Z DEBUG [logstash] logstash/async.go:142 3 events out of 3 events sent to logstash host logstash:5044. Continue sending
2018-04-04T11:27:17.006Z DEBUG [harvester] log/log.go:118 File was truncated as offset (174439171) > size (174438794): /data/logfiles/production_access.log
2018-04-04T11:27:17.007Z INFO log/harvester.go:229 File was truncated. Begin reading file from offset 0: /data/logfiles/production_access.log
2018-04-04T11:27:17.094Z DEBUG [harvester] log/harvester.go:468 Stopping harvester for file: /data/logfiles/production_access.log
2018-04-04T11:27:17.094Z DEBUG [harvester] log/harvester.go:478 Closing file: /data/logfiles/production_access.log
2018-04-04T11:27:17.094Z DEBUG [harvester] log/harvester.go:348 Update state: /data/logfiles/production_access.log, offset: 0
2018-04-04T11:27:17.095Z DEBUG [harvester] log/harvester.go:489 harvester cleanup finished for file: /data/logfiles/production_access.log
2018-04-04T11:27:17.108Z DEBUG [registrar] registrar/registrar.go:200 Processing 3 events
2018-04-04T11:27:17.108Z DEBUG [registrar] registrar/registrar.go:193 Registrar states cleaned up. Before: 1, After: 1
2018-04-04T11:27:17.108Z DEBUG [registrar] registrar/registrar.go:228 Write registry file: /usr/share/filebeat/data/registry
2018-04-04T11:27:17.330Z DEBUG [registrar] registrar/registrar.go:253 Registry file updated. 1 states written.
2018-04-04T11:27:17.895Z DEBUG [logstash] logstash/async.go:142 3 events out of 3 events sent to logstash host logstash:5044. Continue sending
2018-04-04T11:27:18.057Z DEBUG [registrar] registrar/registrar.go:200 Processing 4 events
2018-04-04T11:27:18.057Z DEBUG [registrar] registrar/registrar.go:193 Registrar states cleaned up. Before: 1, After: 1
2018-04-04T11:27:18.057Z DEBUG [registrar] registrar/registrar.go:228 Write registry file: /usr/share/filebeat/data/registry
2018-04-04T11:27:18.111Z DEBUG [registrar] registrar/registrar.go:253 Registry file updated. 1 states written.
2018-04-04T11:27:21.032Z INFO [monitoring] log/log.go:124 Non-zero metrics in the last 30s {"monitoring": {"metrics": {"beat":{"cpu":{"system":{"ticks":2130,"time":2138},"total":{"ticks":6510,"time":6524,"value":6510},"user":{"ticks":4380,"time":4386}},"info":{"ephemeral_id":"c6ba2b0c-9412-4e0c-946e-35bd760ff108","uptime":{"ms":1230018}},"memstats":{"gc_next":5815936,"memory_alloc":4472304,"memory_total":944266416,"rss":143360}},"filebeat":{"events":{"active":-5,"added":53,"done":58},"harvester":{"closed":1,"open_files":0,"running":0},"prospector":{"log":{"files":{"truncated":1}}}},"libbeat":{"config":{"module":{"running":0}},"output":{"events":{"acked":57,"active":-5,"batches":13,"total":52},"read":{"bytes":84},"write":{"bytes":7622}},"pipeline":{"clients":1,"events":{"active":0,"filtered":1,"published":52,"total":53},"queue":{"acked":57}}},"registrar":{"states":{"current":1,"update":58},"writes":14},"system":{"load":{"1":3.37,"15":2.78,"5":2.71,"norm":{"1":0.4213,"15":0.3475,"5":0.3388}}}}}}