Edited for clarity.
Just a heads up that may save some poor modder hours of frustration...
I was having a very annoying/baffling/confusing issues where my magic effect keywords were not being applied after casting the spell once.
It would work once but not again!
After I removed the NoRecast flag from the Magic Effect this stop happening.
The wiki says this flag is "not used". However some vanilla spells have this set to be used !!??
My Magic Effects were based on (copied) those vanilla Magic Effects which is why I set the flag to true in the first place.