I've been experimenting the same bug. Seems like Garuda's Dread Mirror can't recast at all. Every single time you try to recast, with a short tap, she cast the Dread Heart. I've playing with the "New" control layout. The one that you need to hold R1 and activate abilities with the 4 front buttons. I've never found the classic layout to work well with the abilities that need to hold the button to interact. Ivara's #1, Vaubro #2 (after his rework), etc.