Never worked for me since Patch 10.0 and still not in GW2 UI V 6.0.3.

Message: Interface/FrameXML/SpellFlyout.lua:240: attempt to call method 'GetSpellFlyoutDirection' (a nil value)
Time: Fri Dec 2 10:08:11 2022
Count: 2
Stack: Interface/FrameXML/SpellFlyout.lua:240: attempt to call method 'GetSpellFlyoutDirection' (a nil value)
[string "=[C]"]: in function GetSpellFlyoutDirection' [string "@Interface/FrameXML/SpellFlyout.lua"]:240: in function Toggle'
[string "@Interface/FrameXML/SecureTemplates.lua"]:361: in function handler' [string "@Interface/FrameXML/SecureTemplates.lua"]:690: in function <Interface/FrameXML/SecureTemplates.lua:672> [string "@Interface/FrameXML/SecureTemplates.lua"]:704: in function <Interface/FrameXML/SecureTemplates.lua:697> [string "@Interface/FrameXML/SecureTemplates.lua"]:746: in function SecureActionButton_OnClick'
[string "@Interface/FrameXML/ActionButton.lua"]:1175: in function <Interface/FrameXML/ActionButton.lua:1145>
[string "=[C]"]: ?

Locals:

This is a blizzard bug.
Flyout buttons are working only on main action bar till blizzard has fixed it