Where do you get the new dtb ? Have you tried running with the standard dtb from the image ?
I got if from my original Android firmware, I tried standard dtb file too, but the system still reboot again and again, I checked UART log , it looks like:
## ANDROID Format IMAGE
## Booting kernel from Legacy Image at 12000000 ...
Image Name: Linux-3.10.99
Image Type: ARM Linux Kernel Image (lzo compressed)
Data Size: 5519794 Bytes = 5.3 MiB
Load Address: 00208000
Entry Point: 00208000
Verifying Checksum ... OK
Ramdisk start addr = 0x12544800, len = 0x199b83
dectect realtek sdio wifi, config to sdio controller
Multi dtb tool version: v2 .
Multi dtb detected, support 8 dtbs.
aml_dt soc: m8m2 platform: n200 variant: sdio
dtb 0 soc: m8 plat: k200 vari: 2gsdhc
dtb 1 soc: m8 plat: k200 vari: 2gsdio
dtb 2 soc: m8 plat: k200 vari: sdhc
dtb 3 soc: m8 plat: k200 vari: sdio
dtb 4 soc: m8m2 plat: n200 vari: 1G
dtb 5 soc: m8m2 plat: n200 vari: 2G
dtb 6 soc: m8m2 plat: n200C vari: 1G
dtb 7 soc: m8m2 plat: n200C vari: 2G
Not match any dtb.
Flat device tree start addr = 0x126de800, len = 0x2000000 magic=0x5f4c4d41
Uncompressing Kernel Image ... OK
uboot time: 5086716 us.
EFUSE machid is not set.
Using machid 0xf81 from environment
error: not a fdt
Loading Ramdisk to 1fe66000, end 1ffffb83 ... OK
ERROR: image is not a fdt - must RESET the board to recover.
resetting ...
then system reboot again.
Here the image I tested is "LibreELEC-S812.LAN_100.arm-8.0.2.img" and "LibreELEC-S812.arm-18.0_20180601-LAN_100.img", and the results are same.