Hello everyone. I flashed the OpenMode kernel with L2 fix (zImage_2.6.32.54-openmode_l2fix) and install N9QTweak (but didn't enable any tweaks). After this very hard UI freezes appeared. It constantly twitches and blinks (I shot a video https://youtu.be/U8I8GeKf_NE).
I tried to flash the stock firmware again (DFL61_HARMATTAN_40.2012.21-3_PR_LEGACY_001-OEM1-958_ARM, with and without secure zeroing MMC), but freezes didn't disappear (!).
l also tried to flash various MMC images:
UKIRELAND_EMMC_UKIRELAND, EURASIA_EMMC_EURASIA and NOMAPS_EMMC_NOMAPS,
but nothing helped. After each iteration of the firmware flashing, freezes changes: either weaker or stronger. But they don't disappear completely.
Freezes even in the flash firmware mode and during boot. Also in the firmware mode there are artifacts at the bottom of the display:


Maybe this is a hardware problem?