Have you tried setting the Resolution settings to 480i on the A3 and the TV? If that works, start increasing the resolution settings. I was trying to capture GUI images for a owners manual a few years ago and had a splitter that would not pass CEC with a microHD, but would allow a max of 720p if the TV was set first, then the STB.
I have noticed that CEC often works on one device but not the next, even though they appear to function normal when used with another component.
If an option, maybe try another model of splitter?