For some reason, 'my' music rack does not slip very easily out of the keyboard's holes at all. I think the reason is because there is some 'spring tension' in the wire rack which keeps the rack from slipping out very easily.
Before inserting the two wire prongs into the hole, I must press the two wire rack ends together slightly, which creates some 'spring tension' and keeps the wire stand from slipping out of the holes very easily.
To solve your problem, I might suggest that you pull (bend) the music rack wire "ends" out away from each other just sligtly. Then, when you insert the wire rack ends into the keyboard holes, you will have to bend the wire rack ends slightly inward towards each other (to create some spring tension) which should keep the rack from sliding very easily in/out of the hole.
Thanks for your kind words about my keyboard playing Tom. Maybe I should consider getting into the handyman business as a backup
Actually all the credit goes to our friend Andy for sharing with us his most ingenious solution to the long going KN5000 music stand 'plastic rack' problem.
Tom, please let me know if my suggestion solves your problem of your music rack sliding out of the holes on the back of your keyboard.