cortex m7 STR fail

I am using a STM32H753. I have an ISR that adds up some values in a 32 bit RAM location. The code adds the values and stores in a volatile RAM location. The STR instruction executes but the value is never written to RAM. Attached debugger shows state immediately after the STR instruction wrote to address 0x2400ad7c. Is there something wrong with this code?

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