Malfunctioning SMSL SU-9n

I recently purchased a used SMSL SU-9n on audiogon and long story short the optical/toslink input is malfunctioning but the USB works well. I tested multiple cables, sources, and I looked through the menus for simple solutions to no avail. All of my other cables and components work as intended with the SU-9n taken out of the system. However, when the optical input is selected on the SU-9n the audio cuts in and out at different intervals. Have any of you had this issue?

Here is a link to a YouTube video so you can see and hear the malfunction.

SMSL DAC malfunction


A list of the gear I used for testing. 

     Rogue Sphinx v2 amp
     Elac UB5 speakers

     Oppo 105d
     Caldigit TS3 plus - USB hub
     Macbook Pro
     LG C3 - TV


I’ll stick with Schiit audio for DACs I don’t think Schiit would leave you hanging like SMSL did to me. 

As I've continued to research that is also what I've come to understand. I am frustrated that I was sold a faulty product especially because I specifically purchased it for the functionality of the optical/toslink input. 

Schiit left me hanging,. If you give them good money for a Modi and it fails 1+ years, tough nails. They won’t fix or replace it. I have a couple of S.M.S.L. DACs that always work, one on my TV.

Go to the DPLL settings and change the number.  The default setting is 7. I had the same issue when using optical and the source was my TV.  Changing the DPLL number to 9 fixed the audio cutout