Hello there.. I have been a 'trespasser' in these forums for a long long time, its time to start contributing
The obvious and easier solution is to approach Nokia Care or your Carrier and get it replaced if you can. If that is not an option try the below steps.
I had the same problem where the phone heats up and battery drops by certain percentage (15 to 20 in my case). It usually is an app or some process which makes your CPU run like its on fire. When are you observing this? Is it once or twice a day or does it keep happening regularly? The next time you observe the phone heating up do the following steps one after other until you feel its resolved
1. Do a soft reset (Power + Vol down). If this works then its a very good possibility of Software issue.
2. Block all the unnecessary apps in background
3. Uninstall suspicious apps (Skype is notorious in forums but it was not the reason in my case)
4. Auto sync of Gmail is known to cause heating up as it keeps trying to sync even if there is an issue with data connectivity, turn sync to manual
5. Uninstall all the installed apps and install one after the other (install app, monitor for a day and then install the next)
6. If its still not resolved perform a hard reset (you will lose all your data, take a back up). Don't restore your apps and settings, start afresh and follow step 5 for installing apps.
7. If none of these work the issue may be with the Firmware or worse, Hardware. Now is when you have to make a choice - Take the phone for repair or Flash your firmware to a Country Variant. Flashing your firmware is very risky and may brick your phone. You can do further research on this when none of the above options work.
I took a chance and flashed my 1020 on Sunday, earlier it was Italian Vodafone ROM and I am using the phone in India. So far not even a single Battery drain and Battery life has been closer to my old 720. I am installing one app after other to make sure none of them are rogue.
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