Netgear MR1100 Nighthawk M1 reboot when load traffic

hereThis problem has been discussed many times, but never got any real solution, adminsitrator labeled "resolved" and close all other threads.
I have MR1100-1A1NAS at&t , unlocked.
Firmware Version:12.05.05.00
HW version: 1.0
Using either at&t SIM or T-Mobile SIM, it appears it is working on normal web browser, but when doing a speedtest (sppedtest.net), it cannot finish download test , it starts rebooting.
Some suggested to set the Cellular by Default Change it to "LTE ALL". It makes more stable, but it still does not resolve the problem..
Some suggested to use a better power adapter with QC 2.0, it does nothing to help. I measured the power consumption, it consumes 0.3A, and high traffic load the current is around 0.5A, It certainly is not the power adapter issue.