Greetings again, Kitheren!
Thank you for your patience with the wait for a response to your report. After thoroughly inspecting this matter with Apademak, the development team found no problem with the NM using the information that you provided, considering certain properties of the spells used and the conditions that the NM levels up. If you continue to encounter problems with the NM, I recommend submitting another detailed report in a new thread. Thanks again for your patience!