This is an issue you might come across and find it hard to figure out.

www.wireshark.org/docs/wsug_html_chunked/ChAdvReassemblySect...
This is the official documentation about Packer Reassembly in wireshark

wiki.wireshark.org/TCP_Reassembly
Wireshark supports reassembly of PDUs spanning multiple TCP segments for a large number of protocols implemented on top of TCP. These protocols include, but are not limited to, iSCSI, HTTP, DNS, Kerberos, CIFS, ONC-RPC etc. All in all probably somethin ...

serverfault.com/questions/516401/why-does-wireshark-think-th...
I have a three-way TCP handshake, followed by two FIX logons. (FIX is a protocol used in trading.) The first FIX logon (frame 4) is interpreted and parsed just fine by WireShark, but the second logon (frame 6) is interpreted as a TCP segment of a ...

serverfault.com/questions/516401/why-does-wireshark-think-th...
This is a Serverfault thread on this topic.

www.youtube.com/watch?v=GLw-qXdK1MM
This tip was released via Twitter (@laurachappell). Tired of seeing [TCP Segment of a Reassembled PDU] on your HTTP traffic? Change this one TCP setting to view the true HTTP Response Codes in your Info column. This will speed up your troubleshooting p ...