MSP430F5438A: How can I see the flash memory content in CCS?
I believe the distortion you see may be because you don't erase the flash before programming it again.

You are using the WRITE bit but you must have a piece of code that uses ERASE bit set to erase the block.

With flash you must erase everything as a block before writing. This is the number one issue I see when helping customers do over the air updates and firmware updates.

The other reason is that the data didn't arrive properly for whatever reason.