user menu flyout flickers and disappears when user clicks her name the first time (Firefox)

[MerelATDigipolis]

Describe the bug

When a user is logged in and clicks her name in the user menu for the first time, the flyout appears briefly, flickers and disappears. It is not possible to select the logout option.

To Reproduce

1. Go to http://crs-v-front-office-a.antwerpen.be/organizations/overview (only accesible through VPN)
2. Log in using your EID or Itsme.
3. Click your name next to the avatar in the upper right corner.
4. You see the flyout briefly, it flickers and disappears again before you can click it. This only happens on the first click. On following clicks, the flyout behaves normally.

Expected behavior

The flyout appears and stays put until the flyout is clicked and the user logfs out or the user clicks another part of the screen and the flyout disappears again, aka the behaviour when you click your name a second, third, ... time.

Screenshots

screencapture on google drive

OS (please complete the following information):

• Device: Laptop
• OS: Windows 10
• Browser Firefox, also tested in Chrome, it works fine there