This anomaly applies to IC Rev. Engineering A, build codes QFAA-AA0, QFAA-AC0, CGAA-AA0.
The Code RAM reads as zero and can't be written.
Always.
The Code RAM will appear to be corrupted.
Code RAM is located at address 0x0800_0000. Adjust your IDE project file/linkerscript/scatterfile so that the Code RAM is located at 0x0800_0000.