Sounds more like the disc,the disc could be warped,so in a way,used to work but is now damaged without looking damaged,other than the ability to try the disc on another saturn,i would suggest burning a copy and doing the swap trick,if the game loads up and works then it's most prolly the disc,if that too gives the same error then there is something more problematic going down.
At that point it's best to look at the lens or motor,check youtube for saturn repairs with the lens,there are a few things you can do to improve it and it may then get the game working,if not then it could be other hardware related and if this is the case it would then be hard to pin point the problem,i recommend you first try a burned copy with the swap trick if you have no other means to play the backup,this will answer the question quick as to the condition of the original disc,after that it would be cleaning the console and tweaking the lens,after that i would suggest you buy the cheapest saturn loose on ebay as a replacement console,you would do this when you know that it's not the game disc but rather the saturn playing up after the cleaning and so on.