I have a Mecool M8S Pro+ which won't boot up. I can access recovery menu but attempting to load an update or new ROM fails. I can successfully flash box using USB burning tool and have loaded factory firmware as well as third party ROM successfully however during boot-up box locks up. Any suggestions? I've tried every wipe and reformat option in TWRP so I'm out of ideas. Something must be corrupt but unsure what else to try. Any suggestions appreciated.