5.1 sound (center speaker) ubuntu mate 18.04

Hello, i have a problem, got 5.1 sound connected to genius pci card with cmedia8738 chip and integrated sound realtek in both have some random center sound loses only works with 4 speakers and lfe but center is gone, i have to restar and sometimes is working but 80% not working and i have to hand dirty with modifications and a lot a reading through the internet. Is quite annoying this no sound center is…bad.

Curious thing, distros from 2017 never had a problema with 5.1 sound, never!

Thanks.

PS.: all 5 speakers are fine, no problem any kind tested one by one on another computer.