Weird -6061 error with RME RayDAT

[AMZavareei]

Hello,

I've got an RME RayDAT PCIe card connected via lightpipe to three RME 8x8. The card is in a pci lightning chassis connected to a recent model6-core Mac Pro. It works perfectly only if the buffer size is 1024. If I set it to 512 I get an instant -6101 error and playback halt. This makes monitoring difficult.

I've messed around with all the playback engine and IO settings, as well s the RME Raydat HDSPe settings. The converters are set to input sync, and the Raydat is set as the master clock. I've tried turning off everything like the ethernet, spotlight, sharing, etc... I even changed my video card driver and removed my Black Magic video card. I changed from the raydat playback device to an aggregate including it. I put all plugins in an unused folder. I've done just about anything a few hours of googling that error recommended.

I also have 2 quad UAD-2 cards installed. I even tried removing them.

Still, everything is fine just with a 1024 buffer size, but that's it.

This is Pro Tools 10.3.10 on OS X 10.9.5.

Any help would be much appreciated!