In your toggle switch example, it sounds like the TIU channel has already got power. So, in that case, there will be no WD if you wait more than a couple of seconds after the TIU channel has input power. This sounds perfectly normal.
The WD only comes out for a few seconds when input power is applied to a specific TIU input. After that, any train that suddenly receives power from that channel by a toggle or other connection will not see the WD.
