two step to solve.
1. enter the safe mode by power up the console with the SELECT key pressed. choose the "CHECK PSRAM" to see any error occurred or not. if it said error. please contact your dealer for the warranty.
2. if you get no error in above step. format the SD card with FAT32 and 32KB file allocation unit. download and extract kernel to SD card. check the SHA1 value of the kernel and compare it with the value on the website. if all correct. upgrade the kernel again.
theory:
update kernel stuck 1% have two reasons: chip solder failed and kernel file hash error. execute above steps to exclude them. some older SD card and incorrect format also cause it.