After my previous question, I managed to access and view the NVIC register and unfortunately the rogue interrupts were not enabled, so I have no idea why/how their service routines are being accessed.
screen shot showing that TSI0_IRQHandler was called and, since undefined, went to DefaultISR, which endlessly loops.
Highlighted: TSI0 interrupt is disabled, so should not be firing.
USB0 and UART1 have also been firing, though those are also disabled.
Any insight into what might be causing this would be appreciated!