That weird diagonal line happens in various places when I click off of something to something else. It drives me nuts, it happens in all light themes. But it does not happen when I moved the theme to a Ubuntu virtually machine I have.
Tried restarting and that did not solve it. Thought I would ask before I attempted anything more drastic.
EDIT Happens on a live USB as well. Maybe I am crazy and just never noticed it? lol
EDIT Not integrated GPU only Nvidia
Looking over your screenshot, I cannot find the diagonal line. Can you please point it out?
The blue part of the theme.
I have confirmed it is something to do with Nvidia drivers. It does not do it on the opensource driver.
The issue also does not happen on Wayland.
Ah, I see it now.
Does it do it on any of the Nvidia drivers?
I actually rolled my Nvidia drivers back a week or more ago. The latest were causing a variety of issues for me.
It for sure does it on the 525 and 530 sets.
Probably nothing I can do, just going to use a dark theme for now unless I notice screen tear or something in games. (It is probably doing the same thing in dark themes I just cant see it.)
You might try the 515... I admit, I rolled mine all the way back to the 470 simply because It Worked.
Odd, I really have not had any issues in recent times with them until this (Outside of Wayland anyway)
For me it started only about a couple of weeks ago. Until then, my graphics were always perfect.
I do agree with you that the Nvidia Driver is a likely culprit.
I would try a different background and see if the lines repeat - to mi look like a rain
The rain is intentional. It is the diagonal on blue theme that I believe was the problem here.
I tested various other popular themes and I can not get a similar effect in them. (or any other negative effect) May be something for whoever maintains the Zorin themes to look into.
Dark themes seem entirely unaffected which is odd
Possibly, but I am firmly entrenched in this being a Driver issue.
Once, a while ago, I noticed that the hex color #555555 caused my own screens to blank out occasionally when used in a theme. It was not the theme that was the issue, though... And while I could just change that colors use to #555554 or something - it was still a driver issue in the end.
The color is supposed to fill the .sidebar: selected class and it is not properly rendering.
Interesting, so the specific color might be what is causing the issue.
(I also do not doubt it is the driver causing the issue. Was just thinking the maintainer could find a way around it)
I'm running 525 and have been since it came out ...... haven't noticed any changes ..... 
I did not either until yesterday after running 525/530 for quite a while. Definitely something up with it though because this persists through Ubuntu 22.04 and Zorin on a live USB but only when using the non-opensource driver.
GPU (GTX 1650 Super) gives no indication of issues from projects I rendered, benchmarks I ran, and games I played.
I do intend on replacing the GPU within the next few months more than likely. Switching to AMD
Though I doubt any of you are super interested I thought I would post what I ended up doing. I just could not stand to use the dark theme so I went out looking for a new light theme. Really like this one.
Would have preferred a little more color in it like the default Zorin theme. But overall really good if not quite as good as the Zorin default.
Also wanted to point out this does not happen on my laptop using the same Nvidia Drivers.
I wonder if it may relate to a connection issue. I have experienced something similar - I had one monitor hooked up as HDMI and the other as DP, since I only had 1 HDMI port.
Another case entirely happened when I used an adapter. I have not used a splitter, but I suspect it would have had similar results.
So it may be that the graphics drivers are generally ok; but that the connection is framing them.
I actually do have a pretty complicated audio/video connection setup so if that is possible it would not surprise me if that was the issue. I will test this theory tomorrow or the next day.
Would be an odd way to show itself but who knows lol.
