Any help on this issue?

thank you!

Hi,

This looks like an effect of Anti-Aliasing.

You can try, If turning off Anti-Aliasing in Unreal Edit->Project Settings fixes it:

If setting Anti-Aliasing Method to None fixes it, then you can try using a different Anti-Aliasing Method.

Or what is even better, you could change the material of the affected object the following way:
Enable Render alpha to mask and Render After DOF. Also, the material should be Translucent. And Unlit, or Default Lit.
This is how that looked like in Unreal 4:

Then, if the object is opaque and you are using TAA:

• Select the object.
• In the Detail window, go to the Rendering section.
• Enable Render CustomDepth Pass.
• Set CustomDepth Stencil Value to 16.

If the object is translucent and you are using TAA or TSR:

• Select the object.
• In the Detail window, go to the Rendering section.
• Enable Render CustomDepth Pass.
• Set CustomDepth Stencil Value to 32.
• Go to the material editor by double clicking the translucent material in the Content Browser.
• In the Details window, enable Translucency / Allow Custom Depth Writes.
• Set Material / Opacity Mask Clip Value to 0.

Warmest regards,

As described above, I created a couple of translucent video screens.

The result was a) much better image quality, b) severe jittering.

I unchecked the Aximmetry->Jitter checkbox in that material dialog box, and everything is fine now.

What is this Jitter option supposed to do? The screens are not in front of the billboard; I just put the camera in front of the screen.

Hi,

The Jitter material parameter makes sure that Unreal's TAA or TSR wouldn't shade your material.
You don't have to worry about it being unchecked in your material.

Warmest regards,