When using C++, it is also very important that your build settings match that of Panda and Bullet, or otherwise you could get mysterious crashes like this. If you use an optimize 3 build, make sure that you compile in Release mode and that NDEBUG is not defined.
Also, make doubly sure that you’re not inadvertently mixing an opt3 build with an opt4 build; ie. that an opt4 bullet library is used in an opt3 build or so.