ds-2cd2386g2-i change u-boot bootargs to gain unlimited shell

[rocketracoon]

i have this camera : DS-2CD2386G2-I(U)
then i connected through external uart with linux gtkterm, and i can interact with u-boot by send ctrl+u in the first 3 seconds.
I want full shell to interact with camera, then i first used : printenv , then tried to change bootargs , thes saveenv then launched manually loadk and bootm, but seem that saveenv can't save on bootargs, but can save other keys eg bootdelay.
i want full shell to dump ip camera rootfs block


Printenv result
arch=arm
baudrate=115200
board=nvt-na51055
board_name=nvt-na51055
bootargs=earlyprintk console=ttyS0,115200 rootwait nprofile_irq_duration=on root=ubi0:rootfs rootfstype=ubifs ubi.fm_autoconvert=1 init=/linuxrc KRN_PRT=pri mdio_intf=<NULL> phy_addr=0 mac=3c:1b:f8:e5:65:c0 rst_flag=0 bld_rev=3673745 flash_type=spinand flash_size=128MB dram_size=1024MB devtype=0x2404c chip_id=0x1 nvt_chip_id=0x5021 trspt_mode=0x0 sys_nobackup=1 dram2_size=0x20000000 dram2_base_addr=0x40000000 boot_mode=0 power_mode=0 dram0_size_fast=0 dram0_size_capture=0
bootcmd=loadk;bootm
bootdelay=3
cpu=armv7
dbg=0
ethact=eth_hik
ethaddr=3c:1b:f8:e5:65:c0
fdtcontroladdr=6f9c5e0
gatewayip=192.168.1.254
hostname=soclnx
ipaddr=192.168.1.67
netmask=255.255.255.0
phy_addr=0
serverip=192.168.1.128
soc=nvt-na51055_a32
stderr=serial
stdin=serial
stdout=serial
trspt_mode=0
vendor=novatek
ver=U-Boot 2019.04-svn3673745 (Sep 14 2023 - 20:14:47 +0800)
verify=0

tried :
setenv bootargs 'earlyprintk console=ttyS0,115200 rootwait nprofile_irq_duration=on root=ubi0:rootfs rootfstype=ubifs ubi.fm_autoconvert=1 init=/bin/sh KRN_PRT=pri mdio_intf=<NULL> phy_addr=0 mac=3c:1b:f8:e5:65:c0 rst_flag=0 bld_rev=3673745 flash_type=spinand flash_size=128MB dram_size=1024MB devtype=0x2404c chip_id=0x1 nvt_chip_id=0x5021 trspt_mode=0x0 sys_nobackup=1 dram2_size=0x20000000 dram2_base_addr=0x40000000 boot_mode=0 power_mode=0 dram0_size_fast=0 dram0_size_capture=0'

where replaced init=/linuxrc with init=/bin/sh

then saveenv, then printenv again without success.