Same problem here, I've been testing one with these results:
Power supply 20A, CPU 0.9V, Mem 1.03V, one powerful fan on top of stick to get low temps.
Randomly crashing the higher the frequency the often.
From 796 to max, crashing after few minutes, at most about 1 h
From 756 to 796 same but it sometimes work for some hours
Now I'm testing 744 with 0.76V CPU & 0.85V mem, crashing after several minutes to several hours

Also tested different frequencies with higher and lower voltages but no changes
Having to unplug to get to work again, the miner software is unable to restart the stick

Is it a Moonlander problem or a softare problem?