Mushy and unbalanced sound in dual mono set-up

[franchiser]

I have a dual mono 800 set up (converted from 2 d-prems).  Frequently when I start it up, I hear very mushy (bass heavy) and distorted sound on the left channel and low output on the right (companion) channel.  Switching the amp off and on again has always solved the problem up to now, so it is not that big a deal, but I'd be interested to know if any other denizens of this chat room have seen this problem (it may already be a thread subject under another description) and have a better solution. 

Additional info: I'm running FW 8.1.2, but have seen this in all post-SAM FW versions.  Problem has not yet been reported to Devialet.