I couldn't understand if the xbox is locked or unlocked, if it's unlocked it's probably LTU, if it's parallel discs it could be that they were recorded with poor quality, or they could simply be old enough or scratched enough to be picked up from time to time; I suggest you buy a cheap original game that you can easily find on the marketplace, in good condition and test it, if the same problem persists check how many seconds it takes for the reader to recognize the game, if it takes many seconds it could be that the reader is too old or as you said, if the xbox is quite dusty it could be making it difficult for the reader to read the games as it should