How could a lightsabers bright core be maintained when motion blurred? Without motion blur it looks like this:



With motion blur and shutter 1.0

The core dissolves:



The compositing is similar to Post-processing Lightsabers in Blender
Your core is not bright enough, give the core emission strength between 500 and 1000 and then it should be bright with shutter at 1.0. Do the soft red glow in postpro also.