AC-44 strobe light stopped working

[UPDunsmuir]

Greetings
I have a couple of DCC/Sound AC-44s and one of them has developed a strobe light issue out of the blue.  It has been running flawlessly since it's arrival on the railroad(around the time of release date), shut down the layout and the next day the strobes stopped working.  I have reset the engine several times without strobe success. Everything else seems to be working.  Any ideas or experiences with this issue?