Logstash doesn't process all input files - csv

Question

I'm using logstash to process several Zanox csv exports and export them to elasticsearch.
However, for some reason logstash often processes only some of the input files.
The input files definitely exist in the given directory. To avoid the Logstash Inode buch I've set sincedb_path to /dev/null, stop logstash every day before the new files are downloaded and start it after the downloads have been completed.
Logstash and Elasticsearch are currently on the same server
The first file (1) is the only one that always is being imported. It is a rather big feed with about half a gigabyte.
Also the Zanox csv has a small glitch: the first line starts with a point, invalidating the csv format for this line.
input {
file {
path => ["/var/app/1/*.csv"]
sincedb_path => "/dev/null"
start_position => beginning
type => "1"
}
file {
path => ["/var/app/2/*.csv"]
sincedb_path => "/dev/null"
start_position => beginning
type => "2"
}
file {
path => ["/var/app/3/*.csv"]
sincedb_path => "/dev/null"
start_position => beginning
type => "3"
}
file {
path => ["/var/app/4/*.csv"]
sincedb_path => "/dev/null"
start_position => beginning
type => "4"
}
file {
path => ["/var/app/5/*.csv"]
sincedb_path => "/dev/null"
start_position => beginning
type => "5"
}
file {
path => ["/var/app/6/*.csv"]
sincedb_path => "/dev/null"
start_position => beginning
type => "6"
}
}
filter {
if [type] == "1" {
csv {
columns => [ "title", "price", "image", "deeplink", "color" ]
separator => ";"
}
} else {
csv {
columns => [ "title", "price", "image", "deeplink" ]
separator => ";"
}
}
mutate {
convert => ["price", "float"]
add_field => {"source" => "%{type}"}
}
if ![title] {
drop { }
}
}
output {
elasticsearch{
index => products
index_type => products
host => localhost
document_id => "%{deeplink}"
flush_size => 5000
}
}
What could be the reason for logstash not processing all the files?
EDIT:
Removed CSV processing errors by doing some pre-processing. Now I got the following error in the logstash log:
log4j, [2014-09-11T03:41:50.075] WARN: org.elasticsearch.monitor.jvm:
[logstash-17675126.onlinehome-server.info-13551-4016] [gc][young][1345505][23190] duration [2.4s],
collections [1]/[2.8s],
total [2.4s]/[10.3m],
memory [298.8mb]->[122.3mb]/[483.3mb],
all_pools {
[young] [1.9mb]->[1.2mb]/[133.3mb]
}
{
[survivor] [16.6mb]->[0b]/[16.6mb]}{[old] [280.2mb]->[121.1mb]/[333.3mb]
}