File input fails to consume globbed files

Im running into a really odd issue while using the file input plugin;

Logstash 5.0.2

- 2 folders in the same path, one named 2014, the other 2015 (identical permissions at folder/file level)
- both have identical structures, 1 year worth of logs in each
- im globbing to consume a .log file as each year is split by month then day
- using start_position = beginning and sincedb_path = /dev/null, deleted residual since_db files to make sure
- 2014 is consumed and sent to ES (into the 2014 index), 2015 will not be consumed.
- Putting logstash in verbose + debug, i can see the file globbing shows all files in the 2015 folder
- I can see logstash receiving lines via debug
- Using stdin and catting the globbed 2015 dir, i can capture logs via grok and see them appear in rubydebug stdout. Its not a problem with pattern matching..
- Ive checked my config over and over.. it literally doesn't differ apart from the "2015" string in the file path and index names

Sort of at a loss as to why this is occurring... any support would be much appreciated.