Hi Zorba,
Even original grips had to be fitted to some extent. You may also be dealing with warping or other humidity related changes in the wood.
Should you need to repair a crack again in the future, consider using the water based "Gorilla Glue". I've found this to be very strong and dimension stable over time.
Super Glue is an anaerobic setting
Cyanoacrylate adhesive.
Marc
__________________
Igitur si vis pacem, para bellum -
- Therefore if you want peace, prepare for war.