This phenomenon occurs with LED lamps. It is caused by so-called leakage currents. A simple and inexpensive solution is to unplug the timer from the socket, turn it 180° and plug it back in. This reversal of the phase position should solve the problem. For a complete solution that solves the problem permanently, we recommend using a two-phase timer. These special timers always separate the two phases from each other, which safely eliminates the weak residual lighting.