Itunes "Love" Function - selection dissapering

I have upgraded to Itunes 12.2.2.26 and spent a good while highlighting about 900+ favorite songs through the "Love" rating and then making a smart playlist.

I started this playlist in random mode and played music for about 2 hours. When I came to turn everything off all the "loved" ratings had vanished.

I don't want to spend another few hours reselecting the 900+ songs if Itunes is going to forget the ratings.

Any ideas what is happening ?