During development, I've managed to incorrectly/accidentally configure PTA0 with zero values. This appears to have bricked my unit in such a way that I can no longer download code. Note: The code that is currently on there appears to continue to run.
It appears that PTA0 is used by the SWD and my incorrect configuration has this being configured as a Touch Select Input (TSI).
I have not been able to hold the MCU in reset and recover. What other methods should I try to once again debug the unit?