NSData -> MTLBuffer dropping every other 16 bytes

Catalina, 10.15.7, MacPro 2019 with stock video

I'm creating a Metal Buffer from NSData using newBufferWithBytes:length options:either managed OR shared.
The NSData is static.
When my compute shader tries to read the data (or when I inspect in the debugger) the data is right for 16 bytes, then wrong for 16 bytes, alternatively, for the entirety of the buffer.

Has anyone seen this?

NSData -> MTLBuffer dropping every other 16 bytes
 
 
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