Thank you Adrian for your quick response!
I tried different Ethernet cables (even a short one) without any change. The HAT should be mounted properly. But today, I tried clean install of Open Plotter 4, without installing any updates, and it is working well. Then I updated the Open Plotter apps one-by-one and it is still working. When I update (quite a long list) of other system packages, it breaks down again. So I think that some of the "system" packages (not Open Plotter apps) are somehow breaking it. I will try to investigate further which one of it is causing the problems.
Just the [Object] [Object] error is present even in the fresh install of Open Plotter.
I tried different Ethernet cables (even a short one) without any change. The HAT should be mounted properly. But today, I tried clean install of Open Plotter 4, without installing any updates, and it is working well. Then I updated the Open Plotter apps one-by-one and it is still working. When I update (quite a long list) of other system packages, it breaks down again. So I think that some of the "system" packages (not Open Plotter apps) are somehow breaking it. I will try to investigate further which one of it is causing the problems.
Just the [Object] [Object] error is present even in the fresh install of Open Plotter.