When debugging, sometimes the tooltips are too narrow, so the contents are only partly visible or not visible at all.

I've not found a general recipe to reproduce, but a simple "hello world" program is enough to show the behavior (see attached GIF).

#include <iostream>

using namespace std;

int main()
{
    int foo = 42;

    float bar = foo;

    cout << "Hello World!" << bar << endl;
    return 0;
}

It may occur more often if the tooltip contents have very different width, but I'm not completely sure about this.