My issue was (or appeared to be) the sensor assembly. I brought a COMPLETE replacement part for an iPhone 6G. Once replaced, Apple Boot Loop continued, DFU mode did not work, nor did a hard reset, just a continual boot loop. I removed the stock sensor, camera, shield plate and home buttons from the complete part and replace them with the originals from the broken screen. First boot worked - unsure if this could be a boot hardware initiation issue, maybe some of these component parts fail and cause the Apple loop. Hope that helps, Will RocktScience.co.uk

This must be a power related issue - I would replace the battery, removing all necessary components and when reassembling, ensure the connectors are clicked down (if not, this is an indication of the pins wearing or damaged, either on the main board or the flex connectors themselves). If a new battery does not work, you may need to also invest in a new charging port (and sometimes worth testing the charge with a new data sync cable and power plug by connecting it to a wall socket). Other than these steps you may find the power IC is at fault, this is a board level issue and is not easily fixed. I hope this provides some insight! Will

Did anything happen to it prior to this? Water damage? a fall? unauthorised software installation? How old is it and was it brought new or refurbished? These answers would help us answer your issue. Thanks, Will

The display LCD and digitiser are fused together, so if you had to replace the screen it would cost quite a considerable amount - that's if you first check the connectors. Tearing down the device is medium to hard difficulty, you will need to remove most of the components to get to the display. In the age of saving money and time I would suggest returning it for a refund and try to find another on eBay or something (I recently got one for £300 on eBay). In the age of iFixit, tear it down, check the connectors and factory reset the device once again. Hope this helps! Will

I won't ask why you were doing a water test, no good thing can come out of that... You may want to take the device apart and give it a clean with 99% Isopropyl alcohol and a fine tooth brush. I tend to soak in the solution then clean with a brush but you could typically have corrosion within the connectors causing the connection to fail intermittently. Hopefully this will help, if not you might need to replace that part, although my knowledge of Sony Xperia phones is limited, not sure if this would be a solder job or not.. Hope that helps! Will

This may not be a solution but from my understanding there is a resistor on the main board called Board_id, which is responsible for how the devices identifies itself (eg. Apple TV, Apple iPod, Apple iPhone Cellular, Apple iPad Wifi Only, etc) it may be that the water damage has effected this chip/resistor causing it to malfunction in a way.. not sure but would certainly assume it's board related. Sorry I can't be more conclusive, feel free to correct me if I'm wrong on the above! it's a bit of a broken memory! Will

acs- First thing I would do would be to purchase both a new battery and new charging dock connector and not to salvage from another phone. Also, as Tiny suggested, use a wall mains to connect it to charge, you could also rule out the USB sync cable and the wall plug by purchasing new, too! If this all fails you would have ruled out any of the easily replaced components being at fault and I would consider the issue being related to the power IC on the main board; this I'm afraid is considerably more difficult to replace (and where my micro soldering skills are lacking) Hope this helps! Will