Under extrusion when starting outer wall
Based on other comments, answers, and question edits so far, in addition to your original question, I believe there are possibly two things going on here: incorrect retraction settings, including a misunderstanding of which settings are relevant and what they do, and issues related to slow acceleration. Both relate to misdepositing/loss of material.

First, some basics. When the filament is advanced to the point needed to extrude material and print at the intended volumetric rate, it's under significant pressure, compressed between the extruder gear and the nozzle. My understanding is that your printer has a direct drive extruder, not a bowden, so there's far less compression than with a bowden setup but it's still there. This means that, if you try to stop extruding, it's material will continue to come out of the nozzle, just at a decreasing rate, until the pressure dissipates. This effect is reduced but still present if the nozzle is held-against/moving-over already printed material, and heavy if moving over empty space, even moreso if moving across sparsely-filled space like infill where it will bond with the already-deposited material and get "stretched"/"pulled" out.

The idea of retraction is to pull the filament back when the print head is moving to a new location without trying to deposit material, to relieve this pressure and prevent unwanted misdepositing/loss of material, and to reverse the process, putting the filament back exactly where it was when the last printed line ended, the next time it starts trying to deposit material.

The relevant options in Cura are:


Enable Retraction - must be on
Retraction Distance - should be at least 5-6 mm for bowden setups, probably more like 0.5-2 mm for direct drive.
Retraction Minimum Travel - should be 0
Combing Mode - try different settings. Off is probably the best relative to your issues, but hurts your print time a lot for certain models, and can hurt quality in other ways.


Everything else related to retraction is fairly irrelevant, especially "Retract at Layer Change" is a niche option and not typically useful. As I understand it, turning just "Retract at Layer Change" on does not mean retraction is on.

Now, your other issue may be acceleration. Extrusion works best as acceleration speed approaches infinity, because the extrusion rate and pressure needed to extrude will be fairly constant for the entire line/curve. If acceleration is very slow, pressure will be wrong during the start and end of lines. It's likely that, due to high pressure, excess material will get deposited at the end of one line while slowing down, then after moving to start the next line, even if you retract the filament, you'll have insufficient pressure at the nozzle after reversing the retraction to start the next line.

A jerk limit of 5 mm/s is really low. I'm used to more like 20-30 mm/s. You don't say what your acceleration limit is, but it's probably also low. Slow acceleration has minimal impact if your max speed is slow, because you quickly reach the max speed and most of the print speed (and thus extrusion rate) is steady. But if you want to print at high speeds, you need high acceleration. Try and see if you can increase it. Or accept printing at slow speeds.

Another option, if you're open to hacking on your printer, is replacing the stock firmware with a recent version of Marlin with the Linear Advance feature. It does the math to model the filament pressure as a spring, with a spring constant you can tweak, so that it can compensate for varying print speed and end lines with approximately no pressure remaining.