Why does my oscillascope channel fluctuate

[suspension]

I have a Rigol 4 channel analog oscilloscope. Channel 1 does not show a stable wave when connected to the test signal. Please see below for a video. What could be causing this?

[Grandchuck]

Could it be hum pickup?  Did you try switching probes?

[StillTrying]

The first thing to do is to carefully swap the probe at the BNCs to see if CH1 becomes OK, and the wobble moves to another channel. It looks like it could be the probe to me.

Terrible pic. we can't see much.

[suspension]

I have done the probe swapping already and it did not change anything. Could this be due to a damage in analog input circuits related to this channel? I used this channel to test the output of a 230V inverter but not sure if this issue came after that.

Sorry about the picture, I actually used a GIF which shows the fluctuation, but apparently it has been converted to a still image I think.

[Grandchuck]

I have done the probe swapping already and it did not change anything. Could this be due to a damage in analog input circuits related to this channel? I used this channel to test the output of a 230V inverter but not sure if this issue came after that.

That would point to a damaged input.

[StillTrying]

Yes, not looking good, if it was a bad connection on the CH1 BNC I think you'd have found it by now.
What's CH1 plus another one for comparison like both with nothing on the BNCs.
You could try using AC LINE as the trigger source to see if the wobble is mains frequency related, but I don't know how it would be.

[Grandchuck]

What is the resistance from channel 1 ground to the other grounds (from BNC shell to BNC shell)?

[suspension]

Thanks all for the ideas.
I dont know what happened, but the issue went away automatically. I hope it will not come back