[Russ]

Thanks for the pictures, that looks like a nasty piece of cheap kit.

Seconded.
That foam seal doesn't look as though it makes it an IP66 case or even IP anything which is definitely required for anything with an uncoated PCB in it. Moisture will certainly get into that.
Must say it looks a bit breadboard and very much Chinese.

It shouldn't cost any more than around £100 as the parts cost far less.

 

[Russ]

Odd circuit design of the original as the full load current has to pass by the control circuitry......hardly a safe way to do things. In one side and out the other.
At least the replacement keeps power wiring to one end.
The conventional method is to me far safer where a small contactor does the switching with control electronics in a separate module well away from mains voltages.