Impacted versions: 18.2, 18.3 (confirmed on Runbot)

Steps to reproduce:

• Go to the Timesheet module.
• Click input search
• Click on the "Add Custom Group" button.
• The dropdown flickers (keeps closing and reopening) instead of remaining open.

Current behavior:

The "Add Custom Group" dropdown keeps flickering, making it impossible to select any option.

Expected behavior:

The dropdown should remain open and allow the user to choose an option.