OK, as I suspected, your file has windows carriage returns (^M) at the end of each line. So I'm guessing you used a windows editor to edit the file, which automatically added these characters.
I have attached your file with those characters removed. Please try it.
I'm surprised I haven't seen this issue before as I would think it would be quite common to do exactly what you did.
I'm not 100% sure these extra carriage returns are the problem, and I won't be around my tv boxes to test this until tomorrow morning, but I'm pretty sure that is your issue.
extlinux.conf