elphel353-18.104.22.168.30 and earlier
To set the camera in triggered mode you need to set "Program ahead" parameter to 5 instead of it's default value - 3. If not the camera freeze after the first frame.
elphel322.214.171.124.5 and earlier
Cache coherency problem that was revealing itself in imgsrv by (sometimes) returning empty images (actually 1x1 GIF ones) after waiting fro the new image to be acquired. For the error to happen, mmap() (used while processing "img" or "meta" command) had to be called after the kernel wrote the metadata to the circular buffer (that happens during interrupt generated when the image is completely transferred to the system memory), and the mmamp-ed metadata was used before the cached data (kernel writes to cache first for this memory segment) first was flushed out (by other unrelated cache memory usage).
In rev. 126.96.36.199 the bug was fixed by explicitly flushing the used cache line.