Two instances of FMLE at one, lose audio

I run two instances of Flash Media Live Encoder - FMLE at once. The first instance accesses the first Blackmagic card, the second instance accesses the remaining Blackmagic card.
The issue is I lost audio at second instance.
When I reverse the order of executing the instances, the last instance always lose audio.

FMLE version is 3.1.

Blackmagic cards are Intensity Pro.

Does anyone fix this issue? or any work around about it?

Thanks,

Luc