GBTimelapse has stalled several times when controlling a 5D Mk II with a very short time-interval. I traced the problem down to a bug in the Mk II firmware (or maybe in the Canon driver - it's not possible to tell). Even though this bug is due to the MK II firmware, I've found a way to clear the error and continue.
The BUG: a random and intermittent failure to start a bulb exposure. It can happen if GBTimelapse starts a bulb exposure immediately (no delay) after having downloaded the image from a previous bulb exposure. Sometimes when GBT sends a bulb-start command to the camera, the camera returns a value indicating success - but fails to open the shutter! This leaves GBT waiting for an image download that never happens.
My TEST: to reproduce the bug, set a 5D Mk II to RAW images, bulb-time = 2 seconds, and time-lapse interval = 4 seconds. With these settings it takes nearly 5 seconds to do the bulb exposure and download the image. Because the interval is only 4 seconds, GBT tries to capture the next image immediately after the download. The 5D Mk II will fail to capture an image about once every forty images under these conditions.
The FIX: the new GBT version detects the error, clears the Mk II, and continues with the time-lapse. However, the interval for that one image will be a few seconds longer than normal. You will see a message on the main screen when this happens "Bulb Start error 'EDS_ERR_DEVICE_BUSY'", but the time-lapse will continue.
TIP: although the error is fixed, it's best to avoid the situation - I suggest not pushing it. Make sure your time-lapse interval is longer than the total capture time (bulb time + image download time). Just take a test exposure to see what the total capture time is.
