crop mode stops automagically my recording

[adrjork]

Hi everybody,
I can't find a solution to this Magic Lantern issue:
I had a movie recording stopped automagically message (when I tried to shoot in crop mode).
This is my set:
-firmware downgraded to 1.2.3;
-2015Apr28 Nightly Built;
-SanDisk Extreme Pro CF 256GB (ExFAT formatted via OSX Utility Disc - NOT in camera) and this is the UNIQUE card in the camera (ML files are stored in the root directory) so the card is in SLOT 1 (so no Low Level Format option possible);
-Canon Menu: Movie rec. size 1920x1080 24p ALL-I;
-Magnification: x5 (ISO and STOPS change into red on the screen);
-ML Menu: Movie > RAW video ON, 3584x1320;
-lens: 35mm f/2.0 IS USM (in ManualFocus mode, but with stabilizer ON).
I press Start button (camera icon on the screen is red) and immediately arrives the message: movie recording stopped automagically.

I tried other resolutions (always with x5 magnification): 2048x1152 gives me 8 or 9 seconds, then again the stopping message (ISO, STOPS and Camera icons always red).

I tried also 1920*1080 in crop mode: 30 seconds with Camera icon yellow, after that icon becomes red, and at 40 seconds again the stopping message.

Only in FullFrame mode (simply without magnification activated) the Camera icon is green and all works fine.

What could be the issue in crop mode? Perhaps the CF card is not fast enough? (But it declares 150MB/s writing.) Could it be the NOT-in-camera formatting method I used? Perhaps 256GB is too much for the CF card? Could it be something I didn't set correclty in ML menu? Something else?

Please, I hope you want to help me. Thank you so much.

[DeafEyeJedi]

Have you tried pressing the zoom button twice to get into "x10 magnification" and record it?