It is a custom board.
Most code runs. The problem has been gradually more frequent until during software development until it could be considered more or less constant. Note that the break does not occur at a given point in time. It is random but often around the time of and IRQ event.
The board has a serial interface with which a can see resets when the debugger issues the "Stopped due to shared library event" message. If the debugger is not attached the code just freezes.
Since this seems to be a common problem (google) I was hoping there would be a "standard" fix. It feels like some area of memory is accessed in some erroneous manner. What library is referred to?