Typo?

[user202729]

I suspect you should apply this:

--- a/tikz/2d-chi-squared-pdf/2d-chi-squared-pdf.tex
+++ b/tikz/2d-chi-squared-pdf/2d-chi-squared-pdf.tex
@@ -22,7 +23,7 @@
 \begin{tikzpicture}
     \begin{axis}[
         title=$\chi^2_k$,
-        legend style={at={(0.95, 0.95), anchor=north west}},
+        legend style={at={(0.95, 0.95)}, anchor=north west},
         axis x line=middle,
         axis y line=middle,
         grid  = major,

Because there's a bunch of Missing characters warning messages in the log which suggests the anchor specification was not interpreted the correct way.

Same bug with the cdf file.