Boss TU-05 Clip Tuner

Firstly, let me start by saying that I chose this tuner as it's not only from a reputable manufacturer, but it's rechargeable, and as a teacher who uses a tuner a lot this was a great bonus.
Why was/am I disappointed? Well, for a start it gives a different reading depending on whether I choose the chromatic or the guitar setting, which means that one of them isn't accurate. Secondly, it's possible to get the tuner to measure perfectly in tune, but still be able to alter the pitch a fair bit. To get around this, I tune open, then fret 7 and it works really well. Should I have returned it straight away? Yes, but I really couldn't be bothered. On a positive note, the build quality is high, and the clip works really well.