The server is cleaned from old images automatically, which is a script that runs on date.
It does not have any intelligence (yet) to make sure it leaves at least one, no matter how old...
Easy fix... count number of files present, if total > 10 remove oldest...
It's even more easy to just remove the completely unneeded dts-passtrough-patch . There would have be no problem att all if they did it the day a reported the problem on 13-04-2014