I'm the same as @danb in terms of finding it easier to produce more power on the turbo. It's definitely down to the fact that most of my training is done indoors and it takes me about a month of proper outdoor riding to bring it all level.
I've been struggling generally to produce power over the last 6 weeks and dropped my FTP down to 280, a 10% reduction. A visit to the physio has revealed a torn calf muscle. Somewhat relieved, as I'd feared Tendonitis and the recovery time is much less for a tear. Still annoying though.
I mentioned to the physio I was surprised pedal balance data hadn't shown that one leg was injured (I'm quite even and rarely stray from 50/50). The physio basically said that the body makes do and compensates by using other muscle groups.
Anyway, long story short, I hurt my leg :-(