I'm creating a new cdlc, but whenever I try it on Rocksmith I can see weird graphical artifacts around every chord (it looks like the colors of the notes get stretched vertically). I've already checked the chords details and everything seems fine. Any ideas?

Make sure you're using the absolute latest EOF and toolkit betas.  Before the March 7 EOF hotfix, there was a bug in a couple of EOF's chord shape definitions, but the odds of that being the cause here is pretty low because it would mean every chord in your arrangement would have to use one of two specific shapes ("1 1 3" or "3 2 1 1") since you indicated this issue is affecting every chord in-game.

@@raynebc I've followed your suggestions, but sadly nothing changed. To be more clear this is what appears on video 

The next step is to try recreating the chart without dynamic difficulty to rule out anything related to that.  If you used DDC, just skip that step in the toolkit.  If you authored it manually in EOF, make a separate copy of the chart where you've flattened (Track>Rocksmith>Flatten this difficulty) the highest difficulty and deleted the lower difficulties (Track>Delete active difficulty) to get a result of a single difficulty version of the chart.

I've not come across the Flatten feature, what does that do?

It adds the notes from lower difficulties into the current difficulty, basically reverting a dynamic difficulty into a static difficulty again.

So it turns out it had something to do with DD. Until now I was trying to generate the song without using any phrase or section and that must have caused the issue (whether the DD checkbox in the toolkit was checked or not). Weird, I was confident those things would have been added by the toolkit itself. One last question, why does the song come out with DD even if the checkbox is unchecked?

I wouldn't expect that to happen. It may be worth checking to see if @@Chlipouni can reproduce the same issues with your chart files.

Being more precise, this happened before I had added a section to my chart, but now that it has one the toolkit behaves as it should. If it is needed I'll be glad to share my project folder.