Archer c7 v5 wifi & router crashing

i have observed on latest openwrt
when both wifi 2.4g and 5g is enabled
router starts crashing. i checked the system logs and kernel no errors did i find
due to the crash, it affects the ethernet port only 1 device is connected via ethernet port

for a solution, i disabled both wireless bands and it seems not crashing.
i want to enable both the wifi bands
what should i do?

need help
only reason i am using openwrt is for dns over https support
else i would have used tplink stock firmware