It looks in some way as if the starting components for this production line come in 'caisses', and that things are getting held up because there are not enough of them (ties in with 'SHORT')

However, the exact word you need is almost bound to be company-dependent, as you don't know what size, shape, or material these 'crates' are — might be 'bins' or any number of other possibilites...

I'm assmuing it is of course the contents of these 'caisses' that are in short supply, and not the actual 'caisses' themselves — which for all we know might well themselves be the actual starting component!

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Note added at 9 hrs (2012-05-13 20:01:22 GMT)
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It seems to me that the code 'short' means they are short of incoming components; 'self' means that it is this part of the line itself that is causing the hold-up; and 'full' means the output end of the line is full to overflowing; these are logical breakdowns of the production process, so as to try and analyse where the bottlenecks are occurring and try and avoid them.

I was having this discussion just the other day with a friend of mine, who was driven to exasperation by the poor management of the production line on which she works — certainly sounded like something out of a Charlie Chaplin film!