I’m guessing the corner you’re complaining about is where it starts laying down the layer, not the final corner.
You said that’s printed on Fast Speed. I have a bit of missing filamanet after the print head travels on Fast. It seems to be less of a problem on the slower speeds, but I haven’t taken the time to prove it.
The default print settings have Retraction enabled to help prevent stringing, at 6.5mm @ 25mm/s. And higher speeds, that means printing after a travel might be slightly starved of filament for a bit. It is a trade off though. Too little retraction, you’ll get a lot of stringing. Too much retraction, and you get a lot of voids. Print temperature is also a variable; too high of temp, and the filament oozes out during travel.
I’d suggest printing a temperature tower first, then a retraction test. Some users have tweaked retraction down to 1 mm @ 60mm/s. The 3D Printing Walkthrough section 4 has gcode for both tests. I believe that running couple of iterations can help, because changing one can affect the other.