Sonic Frontiers Line 3 preamp issue

I have a Sonic frontiers Line 3 preamp. My problem is that both left channel single ended output connections only produce sound when reverse polarity is selected. When it is not selected, there is very low distorted sound with a buzzing noise. I retubed the preamp to emsure it was not a tube problem but to no avail. If anyone has knowledge of what could be causing this I welcome any and all informartion on what could be causing this problem. If not, would someone please recommend a good repair shop that would be able to know how to rectify this problem.

Thank you.