I recently bought 2 T-Echo Meshtastic devices directly from Lilygo.
Both devices on default settings seem to repeatedly corrupt their flashed firmware. Reflashing them will undo the brick for a couple days, and then it happens all over again.
I have yet to discover what exactly is causing this issue, but suspect it’s beyond my expertise. For it to be happening on default settings, and simply by sitting on a desktop, seems pretty outrageous.
Not familiar with that exact device, but try doing a complete wipe before you flash. Flashing typically won’t clear the internal storage used in a microcontroller. Look for an option like “erase eeprom” or something along those lines.
It’s possible that the lack of a MMU in the nRF52840 can cause memory corruption if the code writes somewhere it shouldn’t because of a programming mistake. I remember that my previous “smartwatch” (the BangleJS 2) which use the exact same chip had some memory corruption issues when it first came out that were likely caused by some bugs in the code.