When reporting an issue, please try to reproduce the issue with just Dominos and Dominos_Config running. Dominos reuses a good chunk of the stock UI, and other popular addons, like Move Anything, like to take control of those parts, too.

Tested with just Dominos + Config, just used bug grabber and bug sack after to grab the error.
This happens after leaving combat and then mounting from what i can tell, i thought it was a dragonflying mount at first but after leaving a dungeon to repair on the yak it also happened.

Addon Version
10.2.11-retail
World of Warcraft Version
Retail

2x [ADDON_ACTION_BLOCKED] AddOn 'Dominos' tried to call the protected function 'OverrideActionBarButton3:SetAttribute()'.
[string "@!BugGrabber/BugGrabber.lua"]:485: in function <!BugGrabber/BugGrabber.lua:485>
[string "=[C]"]: in function SetAttribute' [string "@FrameXML/ActionButton.lua"]:485: in function UpdatePressAndHoldAction'
[string "@FrameXML/ActionButton.lua"]:551: in function Update' [string "@FrameXML/ActionButton.lua"]:1068: in function OnEvent'
[string "@FrameXML/ActionButton.lua"]:302: in function <FrameXML/ActionButton.lua:279>

Locals:
_ = Frame {
RegisterEvent = defined @!BugGrabber/BugGrabber.lua:491
0 =
UnregisterEvent = defined @!BugGrabber/BugGrabber.lua:491
SetScript = defined @!BugGrabber/BugGrabber.lua:491
}
event = "ADDON_ACTION_BLOCKED"
events =

Versions 10.2.13 and later should resolve this.