Indoor activity inaccurate

I play indoor soccer every week for 45 minutes. With my FR235 I consistently got around 3.3-4 km every time. I think that is close to the true distance covered. I recently bought the FR245 music. It is way off when playing indoor activity. It gives me around 0.4 km or something. Absolutely wrong. GPS is off. Has the way it calculates distances changed from 235 to 245?? Any help appreciated.