Having a problem with Legacy system

Where is the command base attached to the track.  You need to check your wiring.  This should not be a ZW-L issue, rather a Command Base or wiring issue if the engine work fine on another command Layout or all your engines started misbehaving.   Maybe a loose connection?  G

Is the Lionel logo on the ZW constant Or flickering?  As GGG suggest it sounds like you lost signal from the base. Check all base to layout connections. 

So you are running conventional engines on a ZW-L using Legacy I think.

From the manual...sorry if you have already re-read all this...

"The ZW-L does not respond to the CAB-2/CAB-1 Remote Controller

Check to see that the Command Base is plugged in and the green light is on. Ensure that a wire is connected between the Command Base "U" terminal and a ZW-L Transformer Command Base terminal (or to the U terminal on a track Lock-On). Turn the power off to the ZW-L and then back on. Check the batteries in CAB-2/CAB-1 Remote Controller. Reprogram the ID# of the ZW-L. Check that the CMD/CONV switch is in the CMD position.

"LIONEL" light is flickering

The Command signal is weak or absent. Check that the Command Base is plugged in and the green light is on. Ensure that the U terminal of the Command Base is connected to the BASE terminal on the ZW-L or to the outside rail of the track."

So you have a steady "LIONEL" light and a steady green lamp?

I take it there is no indicator light on the ZW to indicate that a command has been received other than if it responds to your intended action.