Here they are :
As I said lighting was uniform.
@George : More obvious on this one ? :
LEDs are a DC device, however, that DC voltage can be modulated so that the LEDs can be varied in brightness.
Simply adjusting the DC voltage level will work but it is inefficient. So, whether the power supply is DC or AC, the LEDs are modulated with a varying voltage. This can be low frequency such as 60 HZ or a high frequency or a combination of both.
The cameraās electronics see this varying voltage as a change in brightness and, due to the timing of the shutter, banding is created.
Adjusting the shutter speed to e.g. 1/120s for a 60 HZ country will help but only if the LEDs are being driven from the 60 HZ source.
If a higher frequency is used for the driver, then this will not work.
This effect is most noticeable with electronic shutters because of the read-out time but it can also affect a mechanical shutter (very rare).
A global shutter may be the solution but time will tell.
What I see are shadows. Light coming from the right causing shadows by his brest and belly. The same for the lady.
You just posted a second image. There itās more obvious. But still tricky with that mixed lighting.
George
And shouldnāt the start of the exposure be synchronized in some way with the modulation of the led?
George
This does happen with incandescent lighting but due to the slow response time of the lampās filament, it is not noticed.
LEDs have a very fast response time - 0.001 seconds or less - and this is the cause of the problem. As the LEDs are adjusted in brightness by modulating the supplied voltage, the cameraās electronics sees this modulation and the result is banding.
Yes but with multiple light sources it is a problem. I donāt know if there are any cameras that can sync to the modulation in such a case.
When knowing of mixed light source itās not tricky anymore. 
George
I do know what produces this.
I was providing those images as examples.
I donāt know what the camera does. I just leaned of this subject right now.
What I understood is that the exposure time is fine tuned. Iām just wondering why.
If the exposure is synchronized then the start of the exposure must be the start of the light on wave. That means the camera waits for some impulse to start the exposure.
And the read-out time is being involved.
George
Yes, I am agreeing with you.
I was just giving a bit more detail of why this happens.
Well, there are a few cameras that make an attempt to do this but there are too many variables.
Those are real cases. Not test cases 
.
The flicker reduction menu setting and the ābandingā seen in the sample images posted in this thread are separate problems.
Turning on the flicker reduction setting will not solve the banding issue.
Flicker reduction aims to make the exposure and colours more consistent from one frame to another when shooting under alternating current lighting. Typically the choice of either electronic or mechanical shutter, nor the sensor readout speed do not change the outcome of this issue.
Banding is related to the sensor readout speed when a 100% electronic shutter is used. This relates to the readout speed of the cameraās sensor, but this can be mitigated by the choice of shutter speed if the scenario allows use of a suitable shutter speed that is in sync with the lighting (eg 50/60th with 50/60hz lighting) or by using a camera with a fast sensor readout speed (ie Z8, Z9, A9iii). The A9iii being the only one with a global ahutter which totally eliminates this issue.
To reiterate. Solving one of these problems does not solve the other. They are separate issues. Hope that helps clarifying this 
English is not mine native language but I think that has been suggested. And I just donāt believe that.
Thatās what I thought too.
@JoPoV is showing his examples with the remark that flicker reduction is off, suggesting that this has influence on the banding.
George
My examples, flicker reduction was āonā.
You can choose what you wish to believe, but I can assure you that turning flicker reduction on will not solve the banding issue
Indeed. My mistake.