Relevant Reddit post and images describing the problem.
I did some research: The first version this is happening is 1.1.2.89 ("Added debug console output and more messing with obfuscated names"). Everything before is fine.
This is the corresponding commit.
I don't really understand what is going on here, but this change

         if (obfuscated)
-            targetMethodName ="b";
+            targetMethodName ="d";
         else
             targetMethodName ="colorMultiplier";

could have something to do with it...

Edit: Already fixed!