applescript iTunes 12 enumerate though song

I have this script. it use to work.

Now, When I run it, song after song are displayed in iTunes top middles window (without playing it)

but they are not the one I selected :-)

After it is over, i can see that the right song are modified.

What should I change in this code.

tellapplication "iTunes"

activate

set trackList to the selection of window 1

if ((count trackList) is 0) then

display dialog "No song selected !" with icon caution buttons {"Ok"} default button 1

return

else

display dialog "I will Start !" buttons {"Ok"} default button 1 with icon 1 giving up after 5

repeat with theTrack in trackList

set lyrics of theTrack to "Instrumental only"

delay 2

next track

end repeat

display dialog "Done !" buttons {"Ok"} default button 1 with icon 1 giving up after 5

endif

stop

end tell