I have installed two LED strips in the stairwell and when they are on they are OK, no complaints. But I noticed that when they are off, they still glow a little dimly.
How do I solve this LED ribbon problem?
Is this a normal condition or was a mistake made? How can it be fixed?
This is commonly referred to as the "firefly" effect.
This is a very common anomaly in LED lighting, especially LED strips.
It does not depend on whether the phase is correctly disconnected or not, whether the switches are switched or not.
The slightest residual load causes a "firefly" effect.
It is very common among electricians to solve this problem by connecting a small, inexpensive device in parallel in front of the LED strip (electronic component capacitor).
Some DIY centers sell these directly as an addition to the installation to avoid this effect.