Windows Softphone 20.0.1284.0: disappearing text on dual GPUs—fixed by explicit GPU assignment.

[kevlaboom]

Hi everyone,

I would like to report a reproducible display issue affecting the 3CX Windows Softphone on a computer with two NVIDIA graphics cards.

Text, labels and parts of the interface disappear or render incorrectly, particularly when moving the mouse over controls. The application window remains open, but the missing interface elements make it difficult to navigate.

Environment

• Windows 11, running directly on the computer.
• Two NVIDIA GeForce RTX 5070 Ti graphics cards, with monitors connected to both cards.
• NVIDIA drivers tested: 621.01 and 610.88.
• 3CX Beta package: 3CXDMCC.3CXBeta, version 20.0.1284.0.
• The issue also occurs with the non-beta Microsoft Store app.

Reproduction

With automatic GPU selection:

1. Open the 3CX Windows Softphone.
2. Move the application window to a monitor connected to main graphics card: the interface displays correctly.
3. Move the same window to a monitor connected to the other graphics card: display artifacts appear, and text or controls disappear when hovered over.
4. Move the window back to the first card’s monitor: the interface displays correctly again.

This can be reproduced within the same running application session.

Troubleshooting already completed

• SFC and DISM repairs.
• Uninstalling and reinstalling 3CX.
• Testing both beta and production packages.
• Full NVIDIA driver removal using DDU, followed by driver reinstallation.
• Testing a different NVIDIA driver version.
• A clean Windows reinstallation.

The remaining 3CX issue persisted through these steps.

Confirmed workaround

Explicitly assigning 3CX to GPU1 in Windows Graphics settings resolves the issue. With that assignment in place, I can move the application across monitors connected to either graphics card without the artifacts returning.

The distinction is therefore:

• Automatic GPU selection: artifacts occur on displays connected to one of the cards.
• Explicit assignment to GPU1: the application renders correctly across all displays.

This points toward an interaction involving GPU selection or cross-adapter rendering, although I cannot determine whether the underlying cause is in 3CX, the Windows rendering framework or NVIDIA’s driver.

Could your team investigate this behavior and advise whether there is a known multi-GPU rendering issue? Is there a supported application setting to select the rendering adapter or force software rendering for diagnostic purposes?

I can provide a screen recording, screenshots and diagnostic logs privately. Please let me know which logs or traces would be most useful.

Thank you,

Kevin
Solution IT