Sometimes it takes extremely long for me to enter one of my houses and I often have to close the game to "reset" the whole thing.
Is this an issue within the game or is it because of my internet?
You are not alone my friend, it seems to be generally unreliable for me too. Sometimes i will load in within seconds but most of the time i will spend minutes in the loading screen. Sometimes i have to close the game as it refuses to load me in.
This seems to only happen for housing too, quite odd really.