There was recently a change to the LaTex processor within Canvas, they rolled out a new LaTeX processor (Mathman), to replace the old one (CodeCogs). It has the advantage of giving us much crisper images (svg vs gif) as well as much better MathML (which is read by screenreaders, meaning math content is more accessible now than it was previously). It has the disadvantage of not supporting a couple of the LaTeX commands that CodeCogs supported, so a small percentage of equations now render differently. Unfortunately, CodeCogs does not have a comprehensive list of LaTex commands that it supports, so finding out which ones are no longer available is more of a trial and error thing. Here is a list of the commands supported by Mathman, which uses mathjax:

http://docs.mathjax.org/en/latest/tex.html#supported-latex-commands