I ran W10M build 10586.164 on my lumia 620. Did a hard reset , and restored from the backup that was made in 8.1. Had issues on the build like battery drain , used to lag and all , so I reverted back to 8.1 and now restored from the backup file that was created in 10586.164.
Now my 8.1 too had the same issues , battery drain , laggy nature etc. Tried a hard reset on 8.1 like a million times but still no results. Even tried flashing the phone , but no success.
I had a L1020 too which was on 8.1 only , restored from the backup made in 10586.164 (above ) and my 1020 is having the same issues.
Has some system file gone corrupt ? Even flashing the firmware isn't helping..
Did a lot of research on this topic..
Maybe emmc system repair might help ? I have a file named " LUMIA_620_RM-846_BIG_BOOT.mmc " which maybe able to reset the emmc file system but couldn't find any tool to flash this .mmc file.
A tool named as QPST ( Qualcomm product support tool ) does that but it detects my phone as in 'download' mode and it requires 'diagnostic' mode which has been removed from wp8.1.
Any help on this situation ?