Most common reasons for unstable bugs in C++?

Question

I am currently working on a large project, and I spend most of the time debugging. While debugging is a normal process, there are bugs, that are unstable, and these bugs are

Answer 1

• Reading from uncached memory while a cache line is being written back over the memory (This is a right bastard to find).
• Buffer overwrites
• Stack overflows!

The only 3 i can think of at the mo ... may edit later :)