That fact that this does not show up in screenshots suggests to me that this is some sort of video output issue, either with the video card, the cable, or even the monitor itself

I haven't seen this happen with any other game but i will take a picture with my phone next time i see it

Here is what happens

What happens if you run openttd -d driver4? If you are on Windows, you can also run dxdiag and attach the (graphical, or text via "Save All Information") output here.

Also, can you try turning off Hardware Acceleration in Game Options, to see if that makes a difference?
(You need to quit and restart OpenTTD after toggling the option.)

I've run with the driver4 and it happened but it was smaller. I also turned off Hardware Acceleration and the issue disappeared.

DxDiag.txt

So I've done some further setting setting the Vsync setting to on in the Nvidia Control Panel causes this to happen if i turn it off it doesn't happen as well. I turn in on there since i couldn't find a setting in the game as i was getting screen tearing like in #8968 and have my refresh rate set to 60hz as my monitor won't do higher

Can you start the game with vsync enabled (currently not a setting, but we might add that for these cases):

Open either Powershell or Command Prompt and navigate to the folder you installed OpenTTD. Next, run:

openttd.exe -vwin32-opengl:vsync

Does that resolve the issue for you?

I have tried the setting i still get the black bars but they are very thin line now and they only show up for a 1 or 2 seconds and then disappear

What happens if you set the Vertical sync setting in the NVIDIA Control Panel to Use the 3D application setting ? Does that resolve the issue? (I ask this as you mention you tried on and off, but by default is uses what-ever the application sets it to. Makes me wonder if that makes a difference).

i have it set to that right now when i was testing it.

Have tried with openttd 1.11.1 and Nvidia driver 466.11 now i get black boxes without scrolling ingame with vsync turned on having it off fixes it right away

@adamcirillo There have been a few changes since 1.11.1 - can you try 1.11.2 or a recent nightly build to see if they fix the issue?

It is a bit strange that no one else at all has reported this issue...

I have glitching issue that might be related https://milek7.pl/.stuff/ottdglitch.mp4
Seems to happen only on fullscreen with vsync enabled, but I'm not 100% sure.
(Nvidia graphics)

Almost three years later, but we haven't received any further reports about this anymore from other people. Are you still experiencing this issue? Otherwise I would like to close this issue, as we are not really equipped to debug issues between OpenGL and videodrivers :)

Going to close up this issue for now. If you still experience this issue, let us know!