MSP430F5638: Load Program Error - Debug ignores breakpoint

Tool/software:

Custom SBC using the MSP430F5638-IPZ-2, using CCS ver. 12.8.1.00005, and MSP-FET

When loading the program to MCU or debugging, I've been getting the Load Program Error sometimes over the past year or so.

Usually one or two retries fixes it, or power everything down: SBC, MSP-FET, CCS. But it has gotten much worse recently as the code size has grown over time. But code & RAM usage are still well within the MCU limits.

         MSP430:  Flash/FRAM usage is 42084 bytes. RAM usage is 12016 bytes, that's out of 256 KB available for FRAM, and 16 KB for RAM.

Tried: different variants of the code, two different MSP-FET's, different USB ports, ran a registry cleaner & cold booted the PC but problem persists.

Smaller test programs are less likely to have the problem, two error message variants shown below

Error Message 1

         MSP430: Trouble Writing Memory Block at 0x10000 on Page 0 of Length 0x7fc8: Could not write device memory

         MSP430: File Loader: Verification failed: Target failed to write 0x0FFD8

         MSP430: GEL: File: DC2-430-All-01.out: Load failed.

Error Message 2

        MSP430: File Loader: Verification failed: Values at address 0x110F6 do not match Please verify target memory and memory map.

        MSP430: GEL: File: DC2-430-All-02.out: a data verification error occurred, file load failed.

Another annoying problem is if I do get it to load, and run, the debugger will frequently ignore any Breakpoints, run arrows greyed out, Red Terminate button on

ISR's used for RTC B which sets a time base, and Port 3 has six switches, it's IV is decoded for each switch

JTAG connection shown below, from Hardware Tools User's Guide, Fig 2-1 for 4 wire JTAG connection, pins 10,12,13,14 are for back channel connection - not using this

      SBC power from external regulated power supply

      MSP-FET power from USB port