Martin, I have always used Bug tracker first, including this bug. I only post bugs here when I believe they may be really dangerous and I want to make sure people know about them (very rarely). That is why I seem to panic sometimes.
I have submitted 46 bugs and feature requests to the bug tracker, and I have commented just a few of them in these forums. I have submitted also lots of information about this particular bug here, in bug tracker and directly to you and Eloy by email.
On the other hand, I am a computer scientist, as you are, and I have been programming since I was 10 in Basic, Pascal, C, Fortran, Cobol, Lisp, Visual Basic, Assembler (both Intel 8086 and Motorola 68000), machine code, chips, transistors, and even a little PHP and MySQL
The problem is that, right now I am much more a Project Manager than a Programmer.
I have studied very little about PHP and I do not know enough about programming with it. I hope I will find time someday to study PHP and dedicate even more time to code sometimes. Right now, I am very busy with many other things, I am afraid. Coding is very time consumming.
My problem has turned to be a general one, as I suspected. It is very likely to have the Survey graphics lost, and even more, other people are having the missing answers bug.
So, let's handle this in a constructivist and constructive way, and just work together to have this fixed. Moodle is both a very good e-learning platform and a very well designed software, but there is nothing perfect. This is an amazing community of people. Let's keep on collaborating and working together to solve this little things.