Ubuntu Server constantly crashing on Radxa Zero

I bought a new Radxa Zero v1.5 512Mb without EMMC
After lot of testing the only two images I managed to boot were these two images

As I don’t need desktop environment I went with the Ubuntu Server.
I find that image extremely unstable, it freezes from time to time and have to unplug the SBC to reboot it.
And there are some circunstances that make the SBC freeze inmediately like firing speedtest CLI
After that freezes and reboot, I try to find some errors in the logs but there is no indication in the logs that there was an error at all.

Has anybody faced these issues and found a solution??
If not, is the Debian version more stable??

Radxa “Ubuntu” and “Debian” are identical in (in)stability as they have the same hardware interface.