In fact, the external condition of the "refurbished" smartphone was as described - very good external condition, the phone is in mint condition and ready to use. The battery seems to be in good condition too.
After this first good impression, I started transferring the data from my old phone to the new XZ2, and there was a big problem: once it was switched on, on closer inspection, all the network connections (4G/3G/2G, wifi, BT) were unstable, meaning that I lost the connection to the network every 30s. Worse still, it was impossible to make a voice call on the 4G/3G/2G networks without losing the call after a few seconds.
Worse still, I couldn't update the phone's software after downloading the new version (installation failed for no reason).
=> I had to install the Sony Xperia Companion software on my PC and use the "Software repair" menu, which had the effect of:
- do a factory reset of the smartphone
- install the latest software version for the XZ2
Since then, everything has been working fine, with no instability on 4G/3G/2G, wifi or BT connections. I had to restore all my applications, my phone book, various accounts... In short, 2-3 days lost :-(
I don't regret my choice, given the attractive price and the absence of a real hardware problem, but in all honesty, I could have done without this mishap, knowing that the anomaly was obvious after a few minutes of observation, without a SIM card, simply by switching on the smartphone and making a wifi connection.
I don't know how the verification tests are carried out at Back Market in the case of refurbished smartphones, but they deserve to be strengthened.
One final comment, concerning the "express" delivery I paid for, which was supposed to guarantee delivery within 2 working days... Fedex took 4 days to deliver the smartphone, because of a new, inexperienced deliveryman who indicated in the parcel tracking that he had been to my house but had not heard from me, which was simply not true as I was expecting him, and without a delivery notice in the letterbox or a phone call. Finally, after making several complaints on the Fedex website (it was impossible to get a physical person on the other end of the phone), Fedex Express called me on the morning of the 4th day to ask what time I wanted the parcel delivered. I preferred to collect it directly from them. No luck this time with the delivery.
Stéphane