> 
>  I actually now think I know what it is/was. I suspect (haven't  
>  looked in
>  total detail) that the current code ends up making some kind of m17n
>  related conversion (not StandardFileStream) when saving the map so  
>  that
>  the .gz file actually isn't recognized as a gz file (wrong magic bytes
>  in the header) and thus isn't decompressed - so the actual  
>  imagesegment
>  loading then of course fails badly.

could be that since I always get a parsing error kind of...:)
> 
>  Anyway, I just converted that code back to using StandardFileStream
>  explicitly both on save and load and I now think the code does the  
>  exact
>  same "good ole" thing in all versions 3.5-3.9. We will see.
> 
>  I intend to very soon (this weekend hopefully) deploy this code to  
>  both
>  the server and to update the map entry for SqueakMap and bumping the
>  protocol version forcing all clients to upgrade.
> 
>  regards, Göran
>