I have just received a replacement Mavic 2 Zoom as a replacement aircraft.
Yesterday, i managed to link the a/c to the smart controller and fly. However, with a later flight, the a/c failed to link to the S\c.

This morning they linked on startup but then the link failed and I have been unable to re-establish it/.
All my attempts (10 so far,) at updating or downgrading the a/c software have failed.
Logs have been uploaded but they are unhelpful to me.
Any ideas anyone?

Hi!
You might be better off posting your question in the 'products' section of this forum.
That is way more active.
Just create a new thread here : https://forum.dji.com/forum-129-1.html and select the right category / subcategory.

Hi there. We apologize that you're experiencing difficulties. Here are some advice for you to check your aircraft.

First, you can remove the microSD card and upgrade it again. Then please check whether the version of the smart controller and aircraft firmware are updated.

If it is invalid, you can connect to the DJI Assistant software to update to the latest version, and then try to relink the aircraft and controller.

If still unable to succeed, it is recommended to send the drone back to our factory for futher examination. We will try our utmost to help you out.

Here is our repair link for you to check :
https://repair.dji.com/repair/index