W5500 / WIZ850io - sending random 16 bytes frame


I’m using a WIZ850io module to send and receive data to a C# app on a windows computer.
Everything that I want to do eventually works pretty well, but here is the point :

Using the C# app I noticed some random frame, when sending data from W5500 to the PC, I detected some random datas signals which I didn’t ask for, using Wireshark!
I wasn’t able to attach a picture of it, but this is always the same frame with the same 16 bytes payload (I tried to convert it to see if it means anything but without success).

If anyone has ever experienced that or has some ideas on what’s going on, I would appreciate any help!

I am afraid we need more info. If you can not attach pics here (strange) upload somewhere and give a link. Wireshark format log file would also help a lot.