2x RME HDSPe PCI Cards
2x Digiface
Mac OSX 10.9.5 Mavericks - Logic 10.2.0- RME Driver 407
Same Problem with other hard drive in the same Mac: OSX El Capitan - Logic 10.2.4 - RME Driver 408

Set-Up
The two PCIe cards in the Mac Slot 3 & Slot 4 connected to two Digiface, set as Aggregate Device.

Problem
The assignment of Logic Pros inputs & outputs to the two RME PCIe cards is changing randomly every now and then. That means Logics In- & Output Channels 1-26 are either connected to RME PCIe card+Digiface in Slot3 or to the other Digiface and card in Slot4 (Channels 27 to 52 are changing appropriate)
At the moment ALL of the input channels (1-24 and 27-50) only appear in the Slot 3 window in the Total Mix Mixer no matter what I've set in Logics audio preference (means: aggregate device, Hammerfall DSP Digiface (Slot 4) or Hammerfall DSP Digiface (Slot 4)
That means I have my direct spdif DAC monitoring/Logic stereo-out via channel 25/26 from the Digiface connected to the PCIe card in slot 4 but have no direct input monitoring at all via Total Mix because every bloody Logic input channel appears only in the mixer page Digiface/Slot 3 (even if I record via the Digiface connected to slot 4)

Also
In Midi Studio in the OSX MIDI Set-Up the "wired" connections from each of the two HDSP Digiface to their connected Midi Devices (like master keyboard, synths etc.) is getting  also randomly deleted

With this kind of mess and everything in a fixed installation, one Digiface (slot3) installed with an IZ Radar in an iso-box,  I can't just interchange the firewire cable from the two PCIe cards to adapt to the annoying slot roulette (would not work atm anyway with every input channel from both Digifaces going in the mixer page Digiface/Slot 3) .  Means my Set-Up is unusable at the moment and I like to have a quick solution please

Thanks in advance