We've had an annoying issue with my wife's dragonborn bard when trying to play an instrument. This started before Patch 3 and is still happening after HF7. We are playing splitscreen co-op and she controls the Player #1 Tav.
When she attempts to play any instrument, the animation is weird and she gets interrupted immediately (~1-2 secondds.) Her hands light up like she's casting a spell, and she looks like she's starting the whistling and fingersnapping animation you do when you have no instrument. Logs do make it seem like the performance started, but stopped after a few seconds.
It hasn't been game-breaking, but it is frustrating.
...It just occurred to me that she has been using Phalar Aluve all this time. I wonder if it is reading her "Play Instrument" command as triggering the Singing Sword ability, but since there's no buttton to choose "Sing" or "Shriek" it's aborting(???) Will test unequipping the sword, and then other items, and update back if we learn anything.