I tried to show the work here
Looks very sad. Well, not a damn. So at this stage to help you will be very difficult - it is unclear where the problems manifest themselves, you are talking about (talking in General about anything would be more detail), and where shoals made by you when migrating the code to the sandbox.
Of the strange things that can be noted immediately:
1. Use date as key - can't have two events on one date? Well, the recreate component instance at each change of date too, somehow it looks dumb.
2. Data refresh (onDateInfo) - write data sent from a component at some unknown object, always the same (and the instances of the Date is still different). I do not understand, nonsense.
your code - at the very least, adding/removing work, and the data is updated what is necessary (if I understood correctly). Now you can begin to tell you how to reproduce your problem - what to do where to look.