Is this something that is being done automaticly?

I generally use the admin command when starting the server after the wipe
home wipe - Removes all homes.

or go to \oxide\data\ and delete that file: NTeleportationHome.json

I run /wipehomes.

But that doesnt work when you are already in a new map with people having new homes.

Btw last week people werent able to TP to old homes, this week they can. Ive reported the bug

If you dont wipe/delete the file, they will have still the home.
"Btw last week people werent able to TP to old homes" Maybe bc the rquirment foundation was missing?
"this week they can" Maybe because you changed something in the config where a foundation is not reqirement? 
There are Tons of reason why the can TP and not, the best way to tell you is, when you post your config file here.

I have been using that command for at least the last 15 wipes and there are never any homes left to tp to !, Players cannot tp to a /sethome location that is not saved in the NTeleportation.Data json file,
I use a new map on every wipe and the first thing i do is the admin chat command  /home wipe - Removes all homes.
I then type /listhomes and always get the response "you have no homes saved"

The only way a player can tp to an old /sethome coord is if you dont use /home wipe , They might get the unpleasant surprise of being 300 ft in the air and a long way to fall, Or out in the middle of the ocean especially if its a new map,