I recently purchased a Rigol DS1054Z to replace my unpretentious Hantek DSO2C10. Model and Version are at the attached screenshot (pict.1)

. When I tried to calibrate the 10X probe, my Rigol showed a very strange effect (pict.2)

. The upper and lower shelves of the test meander differ significantly in thickness. I did factory reset, reset to default, auto-calibration, but nothing helped. To exclude the influence of the built-in test signal generator, I connected Rigol to an external sawtooth wave generator and saw that the beam thickness gradually changes from the top to the bottom of the screen (pict.3)

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Then I disconnected probe and step by step made vertical offset from top to the bottom of the screen by using Vertical Position knob. The thickness of the beam and the noise changed from min 20mV at the top to max 180-200mV at the bottom of the screen (pict.4)

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The conditions of the measurements were:
- Nothing was connected to the inputs;
- The First channel was ON only;
- Channel menu: Scale – 500mV/Div; Coupling – AC; BW Limit – OFF; Probe – 10X; Invert – OFF; Volts/Div Coarse; Unit – [V].
- Horizontal: Scale – 100us/Div; Dalayed – OFF; Time Base – YT.
- Acquire menu: Mode – Normal; MemDepth – Auto; Anti-aliasing - OFF.
Then I zoomed beam that was at the bottom of the screen to 50mV/Div and 5ns/Div I saw that it's not a statistic noise but continuous wave with 125Mgz frequency (pict.5)

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All of four channels have the same effect. But it appears if only one of any channel is enabled. Switching between AC -DC in the channels menu doesn't change anything. But if choose GND in the channel menu, the beam thickness and noise voltage becomes min (20mV) and not depend on the vertical offset. I guess that the problem is in the all four input amplifiers circuit of DS1054Z.
Is this a defect of my oscilloscope only, or are all DS1054Z like this? If anyone has the same DS1054Z, could you please check how it looks on your oscilloscope?
Thanks in advance,
Boris.
PS: Link to video, but the sound is in Russian language:
https://cloud.mail.ru/public/V893/WAqkPGPP1PSS: Sorry for mistakes. English is not my native language))