I am experiencing an issue when trying to edit a rubric and am hoping someone can help me.

I created a new rubric for a single assignment in my course on Canvas a few weeks ago. All of the students have now submitted their work, and I began annotating their essays and giving feedback. 

When I went to use the rubric values I had set beforehand to score the submissions, however, I just noticed two severe issues. 1) Canvas altered the scores for each of the ratings in a odd way. 2) Is seems impossible to alter the scores that have been erroneously set.

The maximum score that I chose possible for this assignment was 50 points. I set four broad categories and scores according to the level of competency exhibited in the students' work: Exemplary, 50 / Good, 40 / Limited, 30 / and Unsatisfactory, 20. 

Somehow, Canvas saw fit to alter these scores from 50 / 40 / 30 / 20, to 50 / 50 / 50 / 20, which is utterly bizarre.

Additionally, as the rubric is unusable to mark students work as-is, I tried to edit it - alas, to no avail. As I said, the rubric is for one assignment only (not multiple assignments). I tried editing the scores by clicking the edit icon on the rubric itself, and even went through the "Rubrics" link to manage it. In both cases, even when I clicked the pencil (?) icon to edit the rubric, changed the score, and clicked on "Update Rubric," no changes occurred. 

Any ideas?