I think I figured out what is happening....
After wrtining the D-Flash, the CAS4 seems to startup and run its software. This causes errorcodes to be stored inside the CAS4.
I expected the HexTag to cut power after writing, but this seems not to happen.
I had a flashed CAS4, put it into my car, deleted error codes. Then I read D-Flash and flashed the same D-Flash back. After putting it back to my car, there were stored some errorcodes.
Those errorcodes don´t reapper after deletion; so I think, the came up right after flashing.
Reading multiple times always resulted in the same file. But when I read the D-Flash immediatly after flashing finished, the read file is the same as the file I wrote.
This makes me think, the differences are really those errorcodes, caused by a running CAS4, right after flashing.
Another test I tried is to write zeros to the P-Flash before flashing D-Flash. D-Flash then never changed between writing and reading; there were no differences. But after flashing P-Flash, those differences reappered (without touching D-Flash).
This lets me think, the P-Flash seems to start running after a flash and causing my confusion.
Can you confirm, that HexTag leaves powersupply on and resets the CAS4 after flashing D-Flash?