I haven't figured out why it is going wrong yet but it doesn't handle lower case letters correctly.
I have a workaround. Change this line at the end of Morse.cpp:
send(*str++);
to this:
send(toupper(*str++));
which forces it to deal only with upper case.
If you do this, you can remove all the lower case letters from the _morsetab table because it will never use them and it'll save a bit of SRAM.
Pete