So these are the pictures you requested
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Something is broken, it is now quite clear.
Please can you do all again but now only for CH2.
In my last isntructons but jump over step 2.
Before step 3 shut off CH1 and Open CH2.
Select Trigger source CH2.
Other things just as same as before and this piece of wire things now of course CH2.
If there are significant differences compared to the previous ones, show pictures of them.
BTW, it looks weird that even with your "wire in hand" test traces are all only positive related to GND. This is weird.
And image 1. After selfcal and BNC open 1V/div. This extremely "fat" trace show that something is really wrong.
Also in your all previous images I can not see any negative signals, all are in positive side.
In oscilloscope there is 3 voltage bands. I, II and III. 100mV/div is in this band I. (Band I = 0.5mV - 100mV, Band II = 102mV - 1V, Band III is 1.02V - 10V/div)
(this is why I ask different settings, all these use different V band)
Then please do also this.
Set just factory defaults.
Inputs = Nothing connected. Just empty BNC.
After then turn also CH2 on.
After then adjust CH2 to 500μV/div and CH1 also for 500μV/div
Do not adjust vertical position, leave it just center as it is.
Show image.