Raised lips on sharp vertical corners
If the amount of time spent by the head near the corner is significantly longer than what's spent per unit time elsewhere, you will get more extrusion at the corners and thus this effect. High print speed combined with low acceleration/jerk limits give you this effect.

Using a lower print speed should make it go away because it takes very little time to accelerate up to (or decelerate down from) a low nominal print speed from (to) the max cornering speed allowed by acceleration/jerk settings.

Using (much!) higher acceleration/jerk limits can also make it go away, but can cause other print quality problems and even layer shifts.

The Right Fix for this problem is upgrading your firmware to a version of Marlin with the Linear Advance feature and calibrating it. Then the printer automatically compensates for this issue by varying the pressure at the nozzle to get consistent extrusion rate regardless of changes in speed. I've had very good luck with this on my Ender 3, with a calibration constant K=0.6 for PLA and significantly larger ones for flexible filaments (the constant is essentially the spring constant of the filament for the length of filament path between the extruder gear and the nozzle).

If you don't want to replace the firmware, though, increasing acceleration and jerk limits and lowering speed should work ok. Your machine should be able to handle 3000 mm²/s acceleration on X and Y axis, with 10 mm/s "jerk" (the units of jerk are weird because it's not actually jerk; see my question on the topic).