Hello @Arda_Yurdakul,
The right one is Monta Admin Panel, I wasn’t sure either to be honest. 
After a long digging, I think we found the culprit… You have a collection named stats am I right ? This create a conflict between the express routes /forest/stats (used by your stats collection and our internal route stats used for the charts).
If you don’t use the creation of stats records, just comment the post in your stats route.
// Comment the following lines
// Create a Stats
/* router.post('/stats', permissionMiddlewareCreator.create(), (request, response, next) => {
// Learn what this route does here: https://docs.forestadmin.com/documentation/v/v6/reference-guide/routes/default-routes#create-a-record
next();
}); */
We will create a ticket on our side to make a fix but it could take some time in order to have the ressources to find a solid solution.
Really sorry for this hassling issue. We will update this thread once we release the fix. Thank again for your patience.
Kind regards,
Morgan
PS: Tell me if the workaround works for you. 