TMS470 not firing SCI RX interrupt when disconnected from debugger and power cycled

I have an application running on the TMS470MF06607 that uses two SCI ports. One is configured for ~105k baud 8n1 and the other is configured for ~10.4k baud 9n2. The main clock is 10MHz and SCI1/SCI2, which are source from VCLK1, are sourced at 5MHz.

Here is the SciInit function for reference:

void SciInit(void)
{
    // --------------------SCI 1:APP-----------------------
    sciREG1->GCR0       = 1U;
    sciREG1->CLRINT     = 0xFFFFFFFFU;
    sciREG1->CLRINTLVL  = 0xFFFFFFFFU;
    sciREG1->GCR1       = (1U << 25U) /* enable transmit */
                        | (1U << 24U) /* enable receive */
                        | (1U << 5U)  /* internal clock */
                        | (2U << 4U)  /* number of stop bits */
                        | (1U << 1U)  /* asynchronous timing mode */
                        | (1U);       /* address-bit mode */
    sciREG1->BRS        = 29U; // baud = 10417
    sciREG1->FORMAT     = 7U; // length
    sciREG1->FUN        = (1U << 2U) | (1U << 1U);
    sciREG1->DOUT       = 0U;
    sciREG1->DIR        = (1U << 2U);
    sciREG1->ODR        = 0U;
    sciREG1->PD         = (1U << 2U) | (1U << 1U);
    sciREG1->PSL        = 1U;
    sciREG1->SETINT     = (1U << 9U); // Rx
    sciREG1->SETINTLVL  = 0U;
    sciREG1->GCR1      |= (1U << 7U);
    // --------------------SCI 2:DEBUG-----------------------
    sciREG2->GCR0       = 1U;
    sciREG2->CLRINT     = 0xFFFFFFFFU;
    sciREG2->CLRINTLVL  = 0xFFFFFFFFU;
    sciREG2->GCR1       = (1U << 25U) /* enable transmit */
                        | (1U << 24U) /* enable receive */
                        | (1U << 5U)  /* internal clock */
                        | (1U << 4U)  /* number of stop bits */
                        | (1U << 1U); /* asynchronous timing mode */
    sciREG2->BRS        = 2U; // baud = ~105000
    sciREG2->FORMAT     = 7U; // length
    sciREG2->FUN        = (1U << 2U) | (1U << 1U);
    sciREG2->DOUT       = 0U;
    sciREG2->DIR        = 0U;
    sciREG2->ODR        = 0U;
    sciREG2->PD         = 0U;
    sciREG2->PSL        = (1U << 2U) | (1U << 1U) | (1U);
    sciREG1->SETINT     = 0U;
    sciREG1->SETINTLVL  = 0U;
    sciREG2->GCR1 |= (1U << 7U);
}

As you can see, SCI1 is the 9bit application port that is configured to interrupt on RX. SCI2 is a debug port I use to output state information and error messages.

The problem I'm having is that when I run my code attached to the debugger it works fine. When I disconnect the debugger, it continues to work. But if I power cycle the device the code all runs but the RX interrupt on SCI1 stops working.

Here are other things I've tried and notes about the situation:

• I'm using CCS v6.0
• I'm using an XDS100V2 and physically connecting or disconnecting it does not solve the problem
• I've tried changing the optimization level from none to highest -- no change
• I've monitored the POR and RST lines during debug and when it's disconnected and there is no change, though it should not make a difference because I know the code is running
• When disconnected from debug and power cycled the transmit for both SCI1 and SCI2 work fine, but are not interrupt driven
• I've monitored VCLK by redirecting it to ECLK and looking at it on a scope, when in debug or power cycled the clock is solid
• I've checked signal integrity of the RX line on the device PCB and it appears unchanged whether in debug or not
• If I power cycle then attach the debugger without resetting or reprogramming the device (attach to a running target) then the interrupt will start working
• I've tried building in debug/release modes and the outcome is the same

Any help would be appreciated -- this is a pretty interesting and frustrating problem.