[[Fumble]], when used, causes the relevant auras to go to the graveyard instead of remaining on the battlefield attached to the chosen creature.
On a side note, looking at the code, it seems like the following edge-case ruling is not being followed:
The Auras and Equipment that you gain control of must all be attached to one creature that they can all legally be attached to. If they can’t all legally be attached to one creature, they all remain on the battlefield unattached (and Auras among them will be put into their owners’ graveyards). (2018-06-08)
Instead, as many of them as possible will attach to the chosen creature.
{1}{U}
Instant
Return target creature to its owner's hand. Gain control of all Auras and Equipment that were attached to it, then attach them to another creature.
[[Fumble]], when used, causes the relevant auras to go to the graveyard instead of remaining on the battlefield attached to the chosen creature.
On a side note, looking at the code, it seems like the following edge-case ruling is not being followed:
Instead, as many of them as possible will attach to the chosen creature.