loss of signal every 12 seconds on scheduled recordings

[dirk362]

Environment
3 x PCI PCTV 4000i dual DVB-S
1 x PCI-e TBS 6981 dual DVB-S2
Windows 7 x64 SP1
Latest TBS and PCTV drivers
AMD PhenomII X6 1090T 3.2GHz
650W PSU
2 x 1TB WD HDD, 2 x 2TB WD HDD, 2 x 2TB Samsung HDD
8 Instances of DVBDream 1.7a (latest download to correct bugs)
5 instances record to 1 drive, 3 instances record to another drive.

Schedule is set to start a new instance of DVBDream one per minute, and to record (in some cases multiple channels on same transponder). All scheduled instances are set to run render-less, minimized, with quit at end. I quit given machine powers off automatically via schedule about 30 mins after all recordings complete (to save power & money).

If I manually start all instances, set them to the channels I want, turn off render etc, and record - all works fine.
If I run these as scheduled recordings (therefore run by Windows Task Scheduler), one of the 8 instances (usually 4th) will fail with a loss of signal once every 12 seconds.
If I change cables, or scheduled sequence etc, effectively the problem stays in that it's usually the 4th instance that doesn't work. Meaning it's not cabling, LNB, or settings (as best I can determine).
All instances have all modules disabled, and all settings that might impact performance disabled as well.
All instances have Video & Audio Codec set to Windows 7 MPEG2, with Enhanced Video Render and Default Direct Sound device.

I thought power, but then why would manually doing the recording work fine...
Packet Losses increases by 4 on each 12 second blip, and Signal Losses usually (but not every time) increases by 1. No DS resets or T.Breaks.

Any ideas ?

[rel]

sounds strange, I will check and reply soon