Saving Instance like a players's house doesn't work

Size of objects shouldn’t matter?
It’s just that anything you want to save must somehow be converted into a string, and you’ve got about 260k characters.

@Abdelcrepe

When you save data you use the second argument of Instance.new(),
know that parenting the instance separately is comparatively faster. [1]

I’ve also noticed your code is very legacy like, try avoiding deprecated items wherever possible; WaitForDataReady, ::LoadInstance, ::SaveInstance all are deprecated for a good reason, Data Persistence is unreliable.

In your case: if the only possible houses are specific models then save their names in an associative array to a key unique to every player and upon a player rejoining, retrieve the data and find the particular model and load it for the player.