In order to make NPlot as stable as possible we encourage you to report any issues you're having as you find them. Try to send as much information as possible ( to make a good bug report so it can be reproduced and fixed by our developers.
Providing a simple test case with instructions of how to make NPlot fail will be appreciated and you'll more likely get your bug fixed. Just keep in mind that if we can't reproduce it we'll hardly be able to fix it.
You can also post them to the development mailing list though they can be easily get lost or forgotten.