How do you reproduce bugs that occur sporadically?

Question

We have a bug in our application that does not occur every time and therefore we don\'t know its \"logic\". I don\'t even get it reproduced in 100 times today.

Disclaime

Answer 1

all the above, plus throw some brute force soft-robot at it that is semi random, and scater a lot of assert/verify (c/c++, probably similar in other langs) through the code