As per the Walli Manual, supplied by Fibaro with the dimmer:
FIBARO Bypass 2 (FGB-002) is a device designed to work with FIBARO Dimmer 2 (FGD-212) and Walli Dimmer (FGWDEU-111). It should be used in case of connecting LED bulbs or energy saving compact fluo- rescent lamps. FIBARO Bypass 2 prevents flickering of the LED lights and glowing of the turned off compact fluorescent lamps.
In the case of 2-wire connection, FIBARO Bypass 2 allows to reduce minimum power of load required by the Dimmer for correct opera- tion. FGB-002 provides powering of the Dimmer in case of controlling the low loads of minimum power down to 5VA (for cosφ>0.5).
In the case of 2-wire connection do not connect load below minimal power without FGB-002.
Bypass 2 works only in trailing edge mode. Do not con-
nect the Bypass 2 to the Dimmer operating in leading edge mode.
Bypass 2 is sensitive to the frequent changes of the
state of Dimmer (alternate switching on and off). Sig- nificant changes in brightness should not be performed more than once per second.