Don’t know if anyone else has this problem with their dual extruder but when one of my head’s filament is idle for a long time the point where the filament enters the extruder becomes weak from bending back and forth when the X axis moves and it eventfully breaks. Maybe the issue is because of where my spools are on top of the enclosure my TAZ5 is in. In any case I fixed the problem by adding a simple support bracket to my dual head. I no longer have broken idle filament.
Before the bracket
With the 3D printed bracket installed (yes it clears the top of the TAZ frame). The OEM screw was replaced with a M3x30 screw and the bracket is held on with a wing nut. The bracket does not have to be removed to change filament. The holes in the bracket have to be large enough so the guide tube can move freely at all Z axis heights and X axis positions.