The answer of <show_order ... what="source"/> contains sometimes no source element

In JOE exists in an order menu the "show configuration" function. This calls <show_order order="..." what="source"/> and will show the source element of the answer.
When I have an order which is stored in the SCHEDULER_ORDERS table after terminating the JobScheduler (e.g. the order state is unequal its initial state) then the answer of <show_order ... waht="source"/> doesn't contain (almost always) a source element.
You get the same situation when you abort and restart the JobScheduler.
JOE shows only the message: The source of the order object ... could not be read.