because with the previous firmware this issue was not there.
if the issue disappears with the previous firmware this could confirm that the problem is in the new firmware. Only in this forum page we are in 3 with this issue and it's strange that all 3 are defective units.
I have seen this 3 times with 7.6.1.20.
First time when I first update previous. Then I did many kind of other things (test images etc) with scope using many functions and suddensly I note that Ch2 disappear when 10mV or 5mV/div. First what I did I reboot. Same. Then I selfcal. Then ok. Later, same again but Ch1 and at this time I can not be sure if scope was booted because it was nearly whole day I did many things and then just suddenly I see same issue but Ch1 and it disappear after selfcals.
Now I reboot, run selfcal, reboot, run selfcal and after then, no issue what ever I do and including many boot ups..
Until I think I do really all kind of mad things like "what ever to get it visible". Reboot with flashing buttons, encoders etc... many ways... no issue. Until then I roll back to FW .12 (and heavy try for get this issue visible with this .12 version but I can not see it) and after this then upgrade again to .20
After then with many "random play and boot etc" trying I finally get this issue again with Ch1. And I do not know what exatly tricks issue on. (only I want proof it can exists and take images)
Attached image where can see Ch1 signal is <-50mV. Also with vert pos adj it can not move at all.
There is nothing connected inputs.
After then I did not try so much many things (it IS time consuming... my boot counter show now over 500!)
Without knowing if this is nessessary or not, I run selfcal, boot, selfcal, boot and after then I have not any luck to pop up this issue. Not even with boot time rapid fire Math and not with many kind of use. Just working normally. But, it is proofed it is there in some situation after FW from .12 to .20 so I hope Siglent find what it is and fix it