Thank you for all your answers. I’m actually using 10.5.3 with Kona 3 5.1 NDD when I noticed this problem, and the Raid is internal but not a system drive, I only have footage in it. I tried also other spots of that DPX sequence, and still stops after a minute or so.
But then I tried this, from that QT wrapper I exported a self contained QT movie, at the same specs, 2048X1556 23.98 RGB 10bit, and it plays at least for 5 minutes straight. I checked the properties, and everything matches the wrapper, so my guess has to do with the fact that a wrapper is making a reference to he DPX files, and somehow along the way there’s a bottleneck with that. I tried again to do a system check with the AJA thing utility, and it mantains al least 370 mb/sec.
Another that helped a lot is adding the RAID in the privacy section of spotlight. Then who knows, maybe I have a lot of software running in the background, I should try a clean partition, in the meantime I’ll call AJA
Thanks!