File Grew, but sincedb does not keep up with file

I started logstash in debug against a small directory of files. 3 of the files were written to and consumed. One of the files is continuing to grow.

I see the corresponding logging when the file grows

{:timestamp=>"2016-07-05T16:40:34.528000-0400", :message=>"each: file grew: Data/GrowingFile.log: old size 29458088, new size 31361855", :level=>:warn}

However, the sincedb file is not updated with the new size and the new content is not consumed

This continues and the file is only consumed and sincedb updated on restart

input {
  path => ["/Data/*.log"]
  codec => multiline {
	pattern => "^%{NUMBER:line_num}"
	negate => true
	what => "previous"
start_position => "beginning"
sincedb_path => "logs/sincedb"   
stat_interval => 10