Ray and I have corresponded further about this. We're not entirely sure what happened, but I have learned that you should never edit /usr/bin/dyalog on Linux/Pi. Linux has a system which allows you to select which of several different versions of selected files you want to use - the update-alternatives system.
If on Linux/Pi you wish to alter which version /usr/bin/dyalog points to, simply run
sudo update-alternatives --config dyalog
and select the version that you wish to run.
It is never a good idea to edit the mapl script in the Dyalog installation directory .. we recommend either taking a copy of mapl editing that, or writing your own script and pointing to $DYALOG/mapl .. actually, it's never a good idea to edit any file in any Dyalog installation .. we might overwrite it in the next patch (and this is likely to be true of Dyalog on Windows in the not too distant future too).
