Siglent SVX1015X bizarre trace, please help

[airlomba]

Hello all,

I have a friend that owns a Siglent SVA1015X that present a bizarre behavior... Please, have a look at the picture below. The connection is a simple coax cable (50 Ohm), from PORT1 to PORT2. Then the TG function is activated and the result is as shown on the picture. The frequencies where the slopes appear are always the same. The difference in magnitude is about 4dB.

I would appreciate very much any comment about what could be wrong with this equipment (or its operator).
Thank you all for your time.
Best regards,
Emmanuel.
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[tautech]

Yes I see similar with a new unit freshly updated with the latest V3.2.2.4.0R2 firmware.

When the TG trace is Normalized any errors in flatness are removed.