[Proftpd-user] issues with collecting M2M data

[deva seetharam]

folkswe use proftpd to collect data from M2M gateways. we observe strange behaviours:
1. if there is no iptables protecting it, proftpd works fine for both M2M traffic and  files from workstations.2. if there is iptables, it does not accept data M2M traffic; only the conventional files work.
here are the iptables rules:                                                                                                                                                             
iptables -A INPUT -p tcp -m tcp  --dport ftp -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPTiptables -A OUTPUT -p tcp --sport ftp -m conntrack --ctstate ESTABLISHED -j ACCEPT

iptables -A INPUT -p tcp -m tcp --dport 60000:65535 -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
iptables -A OUTPUT -p tcp --sport 60000:65535 -m conntrack --ctstate ESTABLISHED -j ACCEPT

iptables -A OUTPUT -p tcp  --sport ftp-data -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -p tcp  --dport ftp-data -m conntrack --ctstate ESTABLISHED -j ACCEPT

i have collected some debug info using the following command:
/usr/sbin/proftpd -nd5 2>&1 >& /var/tmp/proftpd-debug-1.log

but, could not get any useful info.
how to debug the issue? please advise. thanks in advance.