Corner Defects after Long Travel  

Corner Defects after Long Travel

Hello all, I have an MK3S+ and have been trying to resolve the corner defects shown in the photo below.  The defects reliably occur after a long travel.  On the opposite side, pock marks occur a short distance away from the corner.  I have tried several things to resolve the issue, including:

• verifying that all the mechanical components are working properly (grub screws properly aligned and tightened, etc.);
• calibrating linear advance and trying numerous values for it (I designed the print in the photo to use different linear advance values at each tier, although the default of 0.04 for my 0.6 mm nozzle appears to work best);
• using multiple hot end temperatures (although a temp tower shows that my current temp of 215 first layer / 210 each additional layer should work well);
• running various retraction tests (currently using 0.8 mm retraction distance, 35 mm retraction speed, 50 mm deretraction speed - this higher speed helped someone on these forums a couple of years ago resolve a similar issue, but it is not fully resolving mine);
• varying Z-hop (the photographed print had 0.4 mm of Z hop);
• running several extrusion multiplier tests (current setting is right at 1.0);
• drying the filament in a filament dryer; and
• slowing the print speed by 50%. 

Despite all these tests, so far I haven't been able to figure out how to prevent this artifact from appearing.  Any ideas on what I can try next?  I suspect there is a slicer setting I'm overlooking.