Repairing the cupboard door

I've had this cupboard for about 45 years. I think it was in the house when we moved in. When I had the kitchen remodeled it was carried into the garage by the builders. It took 5 of them. The top detatches from the bottom. My husband repainted it to match the new kitchen. The right hand cupboard door is cracked and the panel was in danger of falling out. A new piece of board was added to the back of the door to stabilise it.
This is what it was like when I originally gave it the makeover- https://www.blipfoto.com/entry/3674754