Blender 2.8 - Weird experience with smoke domain I hope someone can help me with this weird issue.

I'm trying to create a sphere that emits fire, like the sun.
I've followed this tutorial.

This is what it should look like:



However, as soon as I copy the object (sphere, forcefield and domain) into my other project, the sun's flames start to look like this:



When I copy the object out into a new project, (after baking of course) it again looks good.

What could this be? I've spend dozens of hours trying to figure it out, recreating it etc, but it always comes down to this. 

I would greatly appreciate anyone's help! :)

I'm using Blender 2.8 and rendering in Cycles.

EDIT:
I re-created the sun following the guide, using a new General blender project. This is the result (which is good):



Now, I've copied that object into my other project.

I didn't change the position or size, and simply rebaked.
After bake, this is the result:



Puzzled as to which settings leads to those blurry, small flames.
At best my end result is this, which seems pretty low res compared to the earlier creation:



As far as I know, I haven't changed anything special with regards to the project settings, but I'm more than happy to try some suggestions / check some settings if anyone has an idea :)

Thanks in advance!
I 'solved' this by doubling the resolution of the domain. Still puzzles me why I have to for a same-sized object, and only in this project.