Question about Avantree Audikast Plus

I have the same Audikast Plus as you and don't know the problem at all!!!
Like Anonymous, I think it's the TV set.
Don't you have a second set of headphones to check this?
Or: Switch on Audikast Plus on the TV with headphone output and then with optical cable or vice versa according to what you have already tried.
I have no other idea, the device has been working perfectly for me for a year or more.

I did not buy this product but the "Avantree Oasis Plus" transmitter, but your problem seems to indicate a fault at the output of the TV set.