Dropdown menus instantly select the option under the cursor on open. MacOS

Summary
On macOS, when I click a dropdown menu in After Effects, the menu opens and immediately selects whichever option is under the cursor’s original position, then closes. It doesn’t happen every time, but it happens often enough to make AE hard to use. Screen recording attached - it happens 3 times in the video. as you can see this only happens sometimes usually back to back when it does.
 

Expected result
The menu stays open until I choose an item.

Actual result
The menu opens and instantly selects the option at the cursor’s position, then closes.
 

What I’ve already tried (no change)

• Changed all trackpad, mouse, pointer and accessibility settings in System Settings
• Tried older versions of After Effects
• Clicking the AE Dock icon / switching apps and back before opening the menu
• Turning off “Displays have separate Spaces”
• Testing on the MacBook’s own screen only
• Tried downgrading AE Version

Please help this is driving me insane.