The wiring of the place is almost certainly fine.
I have a number of (similar) units here in my offgrid home in Australia.
My place is different - I have all CBUS controls - so all my lights are actually through computer-controlled dimmers. The LED lights remain on quite brightly even when turned off.
The reason for this is because the snubbers across the triacs (required to meet EMI emission standards) have enough leakage for these ultra-low power devices to sort of work.
I'd be absolutely unsurprised if 50' or more of cable with parallel conductors (as would be used in 2-way or 3-way wiring) had enough capacitance to leak enough current to light your LEDs, albeit dimly.
The usual "fix" for this in home-automation circles, is to put either a small incandescent lamp (5W pilot for example), or a small capacitor, across the load.