Question Unity UI Pointer Enter and Exit keep triggering in loop even when mouse pointer is stationary

I have a simple arrangement for a card.

The 'Raycast Holder' has raycasting enabled and all others have disabled.
I'm using Pointer Enter and Exit events to determine when the mouse is hovering over a card, but for some reason, the events keep firing in loop even when the pointer is stationary on a card.
There are no other UI Objects that seem to interfere with the raycasting so I have no idea why the card is repeatedly firing the events.
A video of the problem :

You can see the Debug.Logs at the bottom (I have collapse turned on)
Why might this be happening? and How can I fix it?
Any help is appreciated.