Netsys Ductwork - Runtime Error 6: Overflow

Good Afternoon,

I've just completed a ductwork system for a Travelodge hotel. I managed to run the calculation successfully but then I've gone back to fix some ductwork sizes on the top floor and added some dampers. Since I've done this I constantly get a runtime error 6 overflow error and then it crashes. Can anyone help please??

Kind Regards

Pete