928 WP8.1 slow and laggy - Slowmo video added

[greycounciller]

I notice you say you've done Hard Resets and all is as before. It looks to me like your firmware is corrupt. I had an issue on my L920 and no amount of soft/hard resets changed it. You still load the same f/w with the same problem on it. Got it reflashed at a care centre and all was hunky dory after.
That just my 2pence worth.

 

[EspHack]

reinstall the firmware, if you are experiencing this since 8.0 then it has something wrong there, and considering some apps work smoothly then there is no question about it, look for navifirm or something like that and download the current 8.0 firmware for L928, mine is kind of snappy I guess, but I think it was smoother on 8.0, 8.1 added some speed but at the cost of stuttering