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next thing I will try is to resoldier the original current source, and see if these oscillations are still here. it's not a big work to do. they are very similar.
then I will try to capture these oscillations if still there.
the original "current source" is not one in fact. each time you power off-on the device, there are small changes in the voltage supply
and the displayed value is not the same. I find it annoying, and tried to have a more stable current source for that purpose.

I received the pcb, tried the new current source and it never worked dur to these oscillations.

At least we know now that the issue is caused by using the new CS.   maybe?

Thank you for the suggestion.
What about having the network adapter of the VM set to "host-only". What would be the disadvantages of this method compared with dnsmasq you are using (which I am not familiar with)

I use dnsmasq for 2 reasons :

Firstly it lets me selectively forward dns requests. So for example the .home subnet which my network is built around gets forwarded to my local home DNS, so the VM can resolve all of the local machines and devices.

The more important for me is it logs every request and at the end of each day I get an E-mail with a list of domains and which devices attempted to resolve them. This is useful information, but moreso when you are "examining" software to see what it might be trying to do behind your back (like exfiltrating data using DNS requests).

I assume (dangerous, I know) "host-only" sets the VM up such that it's an entirely local network to the host. If that works for you, and the VM isn't able to reach your local DNS then it's probably ok. Originally I had my VMs isolated on a different subnet and only permitted to access the local network, but they were resolving using my home DNS so were leaking data that way. It depends on what you are running and how paranoid you might be about data getting out.

My setup is probably over the top for most, but some of the software I've been looking at tends to use extreme methods to "phone home".

So Finally Found it Elektor Milliohm used two topology PWM pulses and constant current share for reference and an idea

sadman

I made the prototype on a perfboard, with the original "current source" (in fact it is not one...)
I made a pcb and during that time I thought I would make this new true current source (at least better)
I modify the pcb to be able to have both current sources on the same pcb if anything went wrong I could still use the original one.
I received the pcb, tried the new current source and it never worked dur to these oscillations.

establish if the design performed correctly after the current source was modified the first time round.

Simple yes or no will do.

I totally agree that using an opamp based CS will be superior. However, that needs a complete pcb modification. I was thinking along the lines of minimal modification if there are already pcb's produced. The TL431 can be implemented without much trouble in place of the zener.

It will be useful to see some waveforms and to establish if the design performed correctly after the current source was modified the first time round.

Ahhh Yes you have a good point about making it fairly easy to modify an existing PCB. The various flavors of 431 are one of my favorite parts.. You can get a lot of performance from them for very little cost. Nice little parts they are.

Yes we're still waiting for OP to post some waveforms. 10-20Hz has piqued my curiosity because its quite odd to me. Guess Kripton is busy.. I guess there is no hurry.

[Country]

Country	Romania
Note	Hobby electronics. Trying to learn Pic Basic and how to use it. Thank you!

no, because it tests AC ohms, I want to test DC ohms.
as there are capacitors on supply rails, if you use such an ac ohm meter, it will always tells you there is zero ohms, the capacitor impedence.
using dc ohms meter, you can find shorted capacitors.

i have found this
http://cappels.org/dproj/dlmom/dlmom.html
lock-in amplifier  can be a good solution