Slot games are fair. But I can't really tell because I don't work with them. But from the information you provided, it is possible they are not fair just from the incident you explain. Though it is possible that the slot game can be manipulated and also it can malfunction. It is vise versa. But if any of them manipulate it, the federal government will look towards it, just as they fine them.

Yea it is possible but majority will be from bug or internet malfunction. Apart from that I don't think gambling site will take such Risk of manipulating the slot knowing trie well the penalty.