I want to mine two different coins (different workers on the same pool) at the same time.
I am running 8 MLDs on one Pi.
I have 4 MLDs running each on 2 hubs(which I intend to extend if I get this working).

For this reason I power down one hub and start BFG miner with the first coin I want to mine. It finds the 4 MLDs and starts hashing.
Then I power up the second hub of MLDs and run a second instance of BFG miner with the other coin. It finds the other 4 MLDs and starts mining.

However after a short time the speed of first instance drops down slowly (a couple of minutes) to 1Mh/s per MLD and lower. I shut down this instance and restart it and it is back to 3-4Mh/s per MLD but then the other instance starts to slow down and goes below 1Mh/s.
I can alway repeat this back and forth, the instance that was running before will always end up runnning slow.

I don't see any hardware errors (600 clock) or any other unusual activity.

Anybody have a fix for this or another way to mine two (or more) different coins on one system?