The move to more software-driven approaches moved the payback selection to a software choice within the game’s configuration. A study conducted in 2009 of a few IGT games by University of Waterloo researchers examined the way slot machines were designed and how they achieved their given payback percentages. If a slot was getting changed to a different payback, a different chip would need to be installed same if the machine was getting reset into something else.
Older slot machines would have their paybacks set based on a specific chip placed inside the machine. Starting with Vegas-style (Class III) slots, the design of the games has always made changing paybacks difficult.
Status: Very, very unlikely in most cases definitely not, anyway. One of the most difficult casino urban legends that goes around is that the casino is tracking what you’re playing and adjusting the odds on a machine, or they raise/lower paybacks based on time of day or during special occasions.