There are plenty of bugs in any mathematical software, and a quick internet search will find them for you. You should never ever implicitly trust output from a computer in any case, without some other means of checking it (such as "plugging in the answer"). Even when Euler proved that $\zeta(2)=\frac{\pi^2}{6}$ or that $\gamma$ exists, he also checked it by hand to an insane number of digits. Thankfully, we don't have to do that to check our work.