The most common cause of restarts is batteries that are underrated for the load. Under this scenario, you get into a situation where a weak battery can start the low-power device electronics, but when the dimmer turns on the battery can’t keep up and the voltage is pulled down too low to run the electronics. At that point the dimmer is turned off, and then the electronics can turn back on from the weak battery. It becomes a cycle. As the battery gets weaker, the cycle gets shorter and shorter.
When a channel is stuck on immediately upon applying power, that means the power driver components have failed dead-short. There is protection circuitry in the dimmer, including temperature protection, but prolonged or repeated connection to loads much higher than they are rated for will cause this failure.
Another cause can be wiring that is dead-shorting somewhere. We see many cases where wires are stripped back far beyond where they enter the terminals, and then the bare copper ends up twisted around and shorted.
We can repair the devices, but we must also ensure that (a) the loads are within the limits of the devices, and (b) wiring is neat and tidy.
Intermittent restarts will occur at the same time a dead-short occurs. This is because the power supply itself is shorted out, so the entire thing is without power for some short period and then must restart when the power recovers.