F5 BIG-IP answers with a self-ip that is not associated with that VLAN

But doing a packet dump I can only see the IP from the Internal vlan responding to packets from the Proxy.

again, is the response packet of the request from proxy?

have you ever tried tcpdump on bigip screen? did you see lis=/Common/vs_proxy_return in the line of the response packet?

[root@ve11a:Active:In Sync] config  tcpdump -nni 0.0 -s0 -c 10 port 23
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on 0.0, link-type EN10MB (Ethernet), capture size 65535 bytes
02:59:05.266764 IP 192.168.207.54.63243 > 172.28.24.10.23: S 1191863643:1191863643(0) win 8192 (mss 1260,nop,wscale 8,nop,nop,sackOK) in slot1/tmm0 lis=
02:59:05.267004 IP 172.28.24.10.23 > 192.168.207.54.63243: S 3126593467:3126593467(0) ack 1191863644 win 3780 (mss 1460,sackOK,eol) out slot1/tmm0 lis=/Common/bar
02:59:05.269906 IP 192.168.207.54.63243 > 172.28.24.10.23: . ack 1 win 65520 in slot1/tmm0 lis=/Common/bar
02:59:05.271480 IP 192.168.207.54.63243 > 172.28.24.10.23: P 1:22(21) ack 1 win 65520 in slot1/tmm0 lis=/Common/bar
02:59:05.271500 IP 172.28.24.10.23 > 192.168.207.54.63243: . ack 22 win 3801 out slot1/tmm0 lis=/Common/bar
02:59:05.277238 IP 200.200.200.14.63243 > 200.200.200.101.23: S 4146213709:4146213709(0) win 4380 (mss 1460,sackOK,eol) out slot1/tmm0 lis=/Common/bar
02:59:05.399602 IP 200.200.200.101.23 > 200.200.200.14.63243: S 2699578800:2699578800(0) ack 4146213710 win 5840 (mss 1460,nop,nop,sackOK) in slot1/tmm0 lis=/Common/bar
02:59:05.399625 IP 200.200.200.14.63243 > 200.200.200.101.23: . ack 1 win 4380 out slot1/tmm0 lis=/Common/bar
02:59:05.399647 IP 200.200.200.14.63243 > 200.200.200.101.23: P 1:22(21) ack 1 win 4380 out slot1/tmm0 lis=/Common/bar
02:59:05.476255 IP 200.200.200.101.23 > 200.200.200.14.63243: . ack 22 win 5840 in slot1/tmm0 lis=/Common/bar