A DESCRIPTION OF THE PROBLEM :
The method javax.imageio.spi.IIORegistry.getDefaultInstance() is not thread safe. If there are 2 threads that call this on start time there can be 2 instances of the default IIORegistry. If both thread register an ImageReaderSpi and/or ImageWriterSpi this can result in the sporadic lost of the registered objects:

Suggested solution is to synchronized the creation:

        if (registry == null) {
synchronized (context) {
registry = (IIORegistry)context.get(IIORegistry.class);
if (registry == null) {
                    // Create an instance for this AppContext
                    registry = new IIORegistry();
                    context.put(IIORegistry.class, registry);
}
}
        }