Ergometer/- 3000m in 6:30min?

Hello,

I have to do the BFT soon and thought I'd start practicing on the ergometer at my gym, where I already train (weight training). No matter what I do, I can't manage the required 27 km/h on the ergometer, let alone 25 km/h. I'm therefore firmly convinced that the ergometer is giving false readings and is simply broken. I sometimes cycle at 400-450 watts and the display shows me that I would only go 23 km/h. Apart from that, you should be able to do this BFT with 170 watts, but on the ergometer 170 watts feels so easy and you only seem to go 18 km/h. The thing also has 25 levels, but it makes no difference whether you pedal fast on level 8 or a bit slower on level 18, you can achieve the same number of watts either way. On a regular bike that I ride outside, I can easily do 30 km/h. The gym has six of them, and they all have the same problem. I also recently had an EKG, where the doctors increased the wattage by 50 watts each time, which made pedaling consistently harder and stayed the same, regardless of whether you pedaled fast or slow. It was all about the revolutions per minute.
Of course, I still train on the ergometer at the gym. Currently, I'm trying to increase my speed to between 250 and 300 watts, and I'm barely managing 2,000 meters in the specified 6:30 minutes. Does anyone know why that could be? Maybe I'm wrong, and the BFT really is that "difficult," but I read online that you should be able to do it easily with 140 watts and the corresponding pedaling speed. I even read about someone here on Gute Question.de who completed this test in 2:50. Incidentally, at the time, I was pedaling at 250 or 300 watts during the ECG, and they said I couldn't handle the load very well.