Relate Bin file (read from uC) to map file
Read back the image from failed MCU (read couple of times if you are not sure if the chip is okay). Then convert the .bin files to Intel Hex (for example: srec_cat input.bin -Binary -Output output.hex -Intel --line_length=44) and use any text diff tool to spot the differences. Addresses are obviously visible in Intel Hex files. Then you can just search the map file for a particular address.

I would dump the flash from suspected boards before doing any other analysis (flash protection can be a problem - if you use it, some MCUs have a backdoor function to facilitate that eg. NXP Kinetis).

If you are experiencing flash corruption in the field I would suspect the firmware in the first place (especially if you store some settings in MCU flash).