[Q] How to flash stock ATT firmware? topic

I have been having a sporadic signal drop issue, it happens when my device toggles to LTE and lasts a couple minutes every time. I just flashed my native bootloader stock firmware (MDL) via ODIN, and still having the same drop signal issue.

Is there a more thorough way to flash back to a stock version? i want to try everything i can at this point to get rid of this pesky signal drop issue, although i am starting to worry my problem could possibly be hardware related...