QUESTION Print head occasionally grinds across the infill

[jrd7777 0]

I'm fairly new to 3D printing, but am able to create adequate proto-types for my audio work.  We print a lot of flat, 12mm thk, "speaker cabinet" walls.  Sometimes we print flat, sometimes we stand the "walls" and thereby print "narrow", tall components.  I had originally thought there was some “build-up issue” associated with a tall configuration, but the grinding happens when we print components "flat" or "tall".  I studied the printer as it was printing and recorded the approximate layer at which the "grinding" was especially bad.  On 99.5% of the "passes" the print head lifts, translates, and restarts printing when it reaches its destination.  However, on or near layer 159 the grinding was especially bad.  So I wondered if it was in the gcode... I used the Preview tool in Cura and found this.   Blue arrows point to "skipped" portions.  The red arrow points to the "print head" and in the direction of travel across the speaker wall.  You can advance the "simulation" and watch the print head "retreat" back to these blue arrows and "fill in" the missed lines.  During this "retreat" is when the nozzle interferes with the existing infill creating the grinding sound.  I watched this behavior happen on a few other layers and, no question the z-motors are not lifting the head.   I have to think this is a Cura, infill-gcode creation issue"?   I’m using Cura 4.8 as my slicer…  need to update at some point but this work fine for our applications.

 

I've included a second and third image to show the print head "retreats" to the blue arrows to complete the infill on this layer...

Any ideas on how to address this or compensate for this occasional, "retreat and drag" issue?