The ONLY TIME(s) I have ANY rendering issues with Lumafusion is if I have video in the project that I have changed the speed on with Lumafusion.
If I chop out a section of video and change the SPEED on that section, chances are - it's going to FREEZE when trying to render and cause me all sorts of headaches to fix.
Today, I needed to change all clips with sped up time to play at MAX 2x speed. Anything over that causes a freeze on export which is a shame as I wanted to use 4x speed on the 2 clips with sped up time in this project.
I never experienced any rendering issues until I starting setting clips to play with faster speeds than 1.0x
Just thought you should know.
What device are you using and what is the source of your footage i.e. resolution and frame rate?