pi zero w as tramsitter

for a couple of years i have used a pi zero w with a tsal6400 led to control devices
i've had no problems until recently
i purchased a no brand name hdmi switcher
i recorded the remote but the pi zero w refused to control the device
just as a test i plugged the led into a pi3
it worked great talk'n to the switcher
the pi zero w and the pi3 have the same version of raspbian
they both use the same version of lirc and the same config files
the led is driven by a transistor that is powered external to the pi's
has anyone experienced this behavior before