It doesn't look like a "scam", usually what a scam suggests is the fact that stake would want to steal your money without having the intention to pay you back. This looks more like a technological error at best, which you could claim is not your fault and I would get it but at the same time its vastly different from a scam as well.

What stake should do about this is an internal investigation about why would a player can play at slots and baccarat at the same time which normally shouldn't be available, however I have never tried to open stake on two tabs and try to bet on the different games at the same time. Maybe, just maybe you could open it up on two different tabs and gamble on two different games as well? If that is possible this looks a lot worse for the accuser and not stake.