I'm not sure if anyone else has had this issue, and my searching around on the internet hasn't resulted in much either. Playing Neverwinter Nights 1, I tend to use Debug Mode to give some of my casters boosts to their ability scores so I can cast more spells per day. I especially Like doing this with Clerics, Druids, and Wizards. However I've noticed that if I increase their ability scores any higher than 128, it bugs out the spellbook and no longer allows me to see any spells at all, even for cantrips, however on the radial menu I can still see the spells that were previously set. Has anyone else encountered this bug, and/or know of a fix to it?

My guess would that stats are stored in signed 8-bit integers. (Or at least it's sometimes treated as signed)

If you use a value higher than 127 it will be interpreted as a negative number. (Somewhat similar to the infamously aggressive Ghandi bug from Civ 1)

I don't think there's a fix short of a 3rd party bugfix if it exists

Have you tried editing the .2da file for the class so they receive more spells per day/level?