Three tracks of this disk can't be read with a standard DOS due
to an alterated address epilog. The usual $DE $AA was changed to
$DE $XX where $XX is different for each track.

We need to tell DOS to ignore epilogue to get a copy of the original disk:

POKE 47516,234 ($B99C:$EA)
POKE 47517,234 ($B99D:$EA)
RUN COPYA

Here the trick is that the modified bytes are used as keys to decode
the following data read from the disk.

Use a disk editor and look at:

track $00 sector $0C byte $00 and change $A0 $00 $98 - LDX #$00, TYA
to $20 $E0 $42 - JSR $42E0, then write this little routine starting
at byte $E0:

A9 AF - LDA #$AF
85 00 - STA $00
A9 BE - LDA #$BE
85 01 - STA $01
A9 CD - LDA #$CD
85 02 - STA $02
85 03 - STA $03
A0 00 - LDY #$00 \ this is the code we previously changed to JSR $42E0
98    - TYA      /
60    - RTS

This put in the zero page the original modified ("original modified" is
an oximoron?) epilogue byte so the program can go on with the decoding step.