conntrack delete does not stop runnig copy of big file

I have a router with nat port forwarding configured. I launched a http copy of big file via the nat. The http server is hosted on the LAN PC which contains the big file to download. I launched the file download from WAN PC.I disabled the nat rule when file copy is running. the copy of file keep remaining. I want to stop the copy of file when I disable the nat forward rule with conntrack-tool.

my conntrack list contains the following conntrack session

# conntrack -L | grep "33.13"tcp      6 431988 ESTABLISHED src=192.168.33.13 dst=192.168.33.215 sport=52722 dport=80 src=192.168.3.17 dst=192.168.33.13 sport=80 dport=52722 [ASSURED] use=1

I tried to remove it with the following command:

# conntrack -D --orig-src 192.168.33.13tcp      6 431982 ESTABLISHED src=192.168.33.13 dst=192.168.33.215 sport=52722 dport=80 src=192.168.3.17 dst=192.168.33.13 sport=80 dport=52722 [ASSURED] use=1conntrack v1.4.3 (conntrack-tools): 1 flow entries have been deleted.

the conntrack session is removed I can see in the following command. But another conntrack session was created with src ip address is the lan address of the removed conntrack

# conntrack -L | grep "33.13"tcp      6 431993 ESTABLISHED src=192.168.3.17 dst=192.168.33.13 sport=80 dport=52722 src=192.168.33.13 dst=192.168.33.215 sport=52722 dport=80 [ASSURED] use=1conntrack v1.4.3 (conntrack-tools): 57 flow entries have been shown.

I tried to remove the new conntrack but it keep remaining

# conntrack -D --orig-src 192.168.3.17# conntrack -L | grep "33.13"conntrack v1.4.3 (conntrack-tools): 11 flow entries have been shown.tcp      6 431981 ESTABLISHED src=192.168.3.17 dst=192.168.33.13 sport=80 dport=52722 src=192.168.33.13 dst=192.168.33.215 sport=52722 dport=80 [ASSURED] use=1

What I m missing?