Black flicker when launching application on external display on Thinkpad T430

Edit: This issue previously referenced CWM, it seems that the window manager is unrelated. See this comment for an update.

Describe the bug:

When any Fyne application is first launched on Ubuntu 20.04, it renders for an instant, then turns black. Resizing the window makes it resume working in perpetuity.

To Reproduce:

Run any Fyne program.

Screenshots:

Example code:

I used the example here in the video,

Device (please complete the following information):

• OS: Ubuntu
• Version: 20.04
• Go version: 1.13.8
• Fyne version: 1.2.5

cad@enki:~ > uname -a
Linux enki 5.4.0-33-generic #37-Ubuntu SMP Thu May 21 12:53:59 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
cad@enki:~ > cat /etc/os-release 
NAME="Ubuntu"
VERSION="20.04 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal
cad@enki:~ > go version
go version go1.13.8 linux/amd64

I seem to have fyne@1.2.5 installed in pkg/mod/fyne.io.

The WM used is a custom fork of CWM. It does have partial EWMH support, but it is possible there is some event that is being ignored/not created/etc. that might be confusing Fyne somehow. I only see this behavior with Fyne, no other toolkits/programs. Further supporting this theory, I cannot reproduce this issue under a stock Ubuntu 20.04 installation in VirtualBox. This could also be related to compositing (or lack thereof).