Send keyboard shortcut with some modifiers fails on some websites

Describe the bug
Sending keyboard shortcuts to some websites doesn't work depending on the modifier. For example, on Outlook web, if you cursor over a misspelled word, you can press option-down to bring up the spelling suggestions. And if you press this key combo on the keyboard, it works great. But if you assign this as an action to a trackpad trigger or stream deck button, the default behavior (go to end of the line) is performed.

Affected input device (e.g. MacBook Trackpad, Magic Mouse/Trackpad, Touch Bar, etc.):
MackBook Trackpad & Stream Deck tested.

Device information:

  • Type of Mac: MacBook Pro (16-inch, 2021)
  • macOS version: 12.5 (21G72)
  • BetterTouchTool version: 3.821

Additional information (e.g. StackTraces, related issues, screenshots, workarounds, etc.):
I've tried this with the

  • send key down and key up
  • send key down only
  • send key up only
    options and none seem to make a difference.

Testing on a site like Yet another keyboard tester does indeed show that the option-down keys are being sent.