I do agree, this isn’t the Firestore’s fault, same thing would happen if going to FCP directly.
My question back would be why would you put the camera in Tape mode, especially if they were not rolling tape? Never do something on set that has not been tested off set, NEVER!
On the HVX, in Tape mode the [Display Setup] Video Out OSD is also on the Firewire Out, it has to be set to off. (not so on P2 mode)
This is a user error, Know Thy Camera (as Thyself).