When creating new curve node, the child of HDA_Data object is named 'curve' and curve points are stored in 'curve Data' array. However, after unloading and loading the scene, curves are off and you need to Recook to make them appear. This recook renames 'curve' object to something like 'curve7', and after that the 'curve 7 Data' array is empty. So, you have to reopen the scene after adding any curve in order not to lose it. 19.0.507