Thanks all for the feedback. It looks like the resistance setting in the app has sorted it.
I do all my routines in Erg mode. However, for the 8 min FTP test my understanding is that it runs it drops out of Erg mode for the test periods and this happens automatically. This kind of explains why I plateau in terms of power output, feel like I have more to give but the trainer doesn’t compensate.
I looked this morning and tried a few things. First I did a test on the Tacx app at the highest gearing I reached during the tests. At a lower cadence (87 compared to 110) I hit around 305watts where during my botched test it was around 260. Doing the same on the TR app resulted in similar stats.
I then looked at the resistance setting in the app and that is where I think the issue was. During tests I was definitely at 100% of the resistance setting. But the app resistance setting was at 30%. Dialling this up to 50% has made a massive difference and when testing is during a 8 min FTP test this morning I rode the same conditions as a few days ago and hit 289 watt which is more realistic and I didn’t feel like I was spinning out as I was around 90rpm.
I’m still getting odd results during calibrations and I appreciate the points on the Tacx issues which I’ll read up on too.