I am sure this has been discussed quite a few times, but I found a tutorial recently doing the exact same thing as I did, but in my case my logo is messing up!
Here is the link to the workflow: https://www.youtube.com/watch?v=mihkAGfnrWA
This is what it looks like after adding the solidify modifier:
I already recalced the normals of my spline, but besides that it messes up my spline shape, it had no effect.
Any suggestions on how to fix it?