Just a quick post to help anyone in the future who comes across this bug - after a day of tearing hair out over trying to figure out why enabling some code would cause the device to not load whatsoever, I spotted the error in the log output of the GDB Server:
ERROR: Failed to erase sectors 3 @ address 0x00003000 (Algo124: Invalid sector)
It turns out the LPC11A12/101 device map is only configured for 12kb, not the full 16kb flash.
Instead, reconfigure for the LPC11A12/201 (a non-existent device, or at least not listed in UM10527) and writes to the final 4kb flash then work!
Downloading 200 bytes @ address 0x00003000
ERROR: Failed to erase sectors 3 @ address 0x00003000 (Algo124: Invalid sector)
It turns out the LPC11A12/101 device map is only configured for 12kb, not the full 16kb flash.
Instead, reconfigure for the LPC11A12/201 (a non-existent device, or at least not listed in UM10527) and writes to the final 4kb flash then work!
Downloading 200 bytes @ address 0x00003000