Sorry for posting was very wrong topic to talk abt
Do not try to upgrade mainline openwrt from the bpi/sdk version. Make a clean install.
Flash image to sdcard and install to nand from uboot menu (debug uart needed).
Ah,sorry missed that you use R3mini.
This is official instruction:
https://openwrt.org/toh/sinovoip/bananapi_bpi_r3_mini#installation_instructions_for_emmc