It looks similar to a heat creep issue I’m having with the Dual Extruder V3. What’s happening to me is that the heat from the nozzle spreads up the filament to the hobbed bolt, and as the plastic softens the bolt starts to cut the plastic out of the filament instead of gripping and pushing the filament through the hot end. My extrusion looks like the trailing off bit just like at the end of one of your lines, only there is never any recovery- it just stops extruding.
You may have a similar issue only not as dramatic, so while the bolt slips on the filament, it eventually grips it again, but there is a short loss of traction resulting in no plastic moving through the hot end. You can try reducing the print temperature by 5-10 degrees- lulzbot have told me that people are getting better results with this hotend for PLA by dropping temperatures a little; you could point a deskfan at the printhead for more cooling (turn it on AFTER the first layer or two are printed so you still get good bed adhesion). You could also try slowing the print speed.
I would also double check that your coasting setting isn’t too high.
If it’s heat creep, then the print failure isn’t anything related to the size of the lines you’re printing, but rather heat spreading up the filament over time. So you could check that by trying to print something tall- like take a calibration cube and scale it up and just let the printer go. If it’s heat creep, you’ll eventually see the print fail.
Good luck. I can’t get PLA to work AT ALL with the dual extruder V3. Using a desktop fan slowed the problem but didn’t solve it, but if your part is small enough that might fix it.