Consider this code:
console.groupCollapsed("my group");
console.table(data);
console.groupEnd();
Repeat that many times (say, a hundred times), and some of the tables will appear outside their resptive group, while the corresponding groups will appear as being empty. In essence, sometimes, groupCollapsed() may be executed *after* table().
Tested with the latest stable and beta versions, and Firefox 28 on Windows 7.