2500mb/s Negotiated Speed?

I have a SDX with a Peplink Switch attached on its LAN.
The SDX has been set to 100Mbps Full Duplex manually to test a LAN side packet loss issue.
The switch shows that 100Mbps has been negotiated on its uplink port.

The SDX however shows this - is it a UI bug?

Yes, it considers a web UI bug. I explained here - https://forum.peplink.com/t/introducing-the-new-ap-one-ax-public-announcement?replyNo=14&replyId=6121e8316b1bec0690026383.