how to fix my panasonic SC-AK 40 aux?

I use my Samsung TV as a computer screen using a HDMI cable between my desktop and TV.
Using a Digital to Analogue Converter and Optical cable I have connected my TV to my "panasonic SC-AK 40" CD stereo system to run all the sound through my panasonic SC-AK 40.
This works really good, except, sometimes, when I'm playing binaural beats from my computer through the panasonic aux to my headphones, the aux just cuts out.
I'm guessing some part of my "panasonic SC-AK 40" is not reading the incoming signal, causing it to cut out.
It might work fine for 3 or 4 minutes then it just turns off.
Any thoughts or suggestions welcome.