I am a music theory professor. I grade homework on my iPad with an Apple Pencil. This is necessary, because we use music notation and not alphanumeric text.

Once I exit and return to an assignment which I've already annotated/corrected, my pen markings are pixelated, don't look natural, and are often displaced from where I originally wrote them. Because I write corrections on images containing a music staff (and note placement is of absolute importance), my annotations often are moved up 1-2 millimeters after I've exited and returned to the assignment. That won't do. 

I've included a file which frankly doesn't show the worst of it (I'm short on time...sorry). My handwriting doesn't usually look that odd. The first few notes should be centered on the second space. When I wrote them, they were absolutely centered. And now they're all shifted up slightly. Sometimes the app shifts them up to the next line. Like I said, that won't do.

Is this a setting on my end? Is there any way to get Canvas to save my natural line-curves and line-placement in my annotations so that my feedback may be helpful to my students?