I've an BQ Aquaris E5 FHD (MTK6592) and today I decided to update to latest firmware version via hard reset using SP Flash Tool, the first time the process was interrupted without reason, so I tried for second time and everything was OK, the phone was able to boot normally. Then I noticed that the serial number was wrong (0123456789ABCDEF) so I powered off the phone and wanted to correct it using IMEI Sn Writer, but for some reason it couldn't connect to the phone, so I disconnected the cable and the phone was not able to boot anymore. The phone seemed bricked, every time I connected it to Windows appeared as "MTK Usb Com (COMx)". I think it had corrupted preloader so I spent hours and hours reading forums and trying to flash preloader with SP Flash Tool without luck. I had read this topic so the last try was leaving it charging and voila! after 1 or 2 hours it booted and showed the battery charging animation with 50% of battery, then I disconnected the cable and connected again and it started charging from empty (0%). I suspect this is because some battery calibration data is lost after unsuccessful flashing, it's strange.