Ok, I had read that one already and... I did not understand it all !
However I had tried all possible export TERM=xxx with xxx in the list of possible tems (ansi, linux etc...) and this did not improve anything.
Logical since the article seems to say you must set TERM to the actual terminal you are using.
The only change I noticed is that some terminals do not allow you to erase the cursor - so I removed the setcursor(0) for the test.
=> I suppose that if lubuntu is delivered with TERM=xterm-256color it is the proper one.
Also note that on the other PC where all is fine (ubuntu) the same defineition applies - TERM=xterm-256color.
So I am still in the dark here :-)