Tool/software: Code Composer Studio
See also: 
I am seeing the exact same behavior as described in 
The MSP430FR5969 shows unexpected behavior when operating off of a 16Mhz HFXT. The original replies to the question before obviously did not understand this point. If you read carefully, the original poster was operating at 16MHz. As the thread has been locked, I cannot reply there, so I'm creating a related question to bring attention to what I am now suspecting is an ERRATA (or a compiler bug).
As far as I can tell, we are operating within maximums. When MCLK is operating off of a 16MHz HFXT, the debugger breaks at random locations.