L1 T4s intermittently cutting out

I see there is a similar post 3 years. During a live performance T4s audio was cutting out intermittently all channels.
1 sax
2 guitar amp
3 vocal shure
4 vocal
when on break, playing music through 5/6 was unaffected and sounded great.

I was powering the Ts4 through the L1 base stand

The next day I set it up and it worked great, however I was only using 2 inputs. Also played a live performance since with sax on #1 and backing tracks 5/6. worked great

I have had the unit for last least 6 years and have never had a problem.

Any suggestions?

Insufficient power? (disclaimer: I am not familiar with the T4s)