Can anyone help me out with why this bug happens?

I have a mage that I dual-classed from a warrior. Fo no apparent reason I lose memorized spells from my book. To the point that every spell from level 1-4 was gone from my book one time. It's a good thing I had skill with weapons!

I have the Dak'kon Zerth blade that I could see could bug that if I were to repeatedly unequip it. But I hadn't done that.

Thoughts? Thanks.

Wich mods do you got? Have you patched your game?

I've patched. I'm only using a couple of the ease of use mods(stackable arrows/potions, quick movies). Nothing else.

You mean they are erased from your book (right page) or from your memorisation screen? (left page) If it is the latter, you may be level drained. When you are level drained, you lose many memorised spells with spell slots.

If it is not, well, you can delete your own spells from your spell book if you have ToB. (erase spell) Maybe you accidentally erased your spells from right page?

Other than that, I have no clue. :( Can you still re-write those spells via scrolls?

This has happened to me on occasion, but always when switching robes if one of the robes is the Upgraded Items Enhanced Robe of Archmagi (this robe adds 1 spell each levels 1-4 among other things).

And only on the left side of the page- my spell picks.

So, e.g., if I replace Robe Archmagi with the Robe of Vecna (or elven chain or whatever) it doesn't just lose the one bonus spell each level but blanks out all spell slots levels 1-4).

Since all your spell slots are erased but only levels 1-4 I suspected this might be the poblem.

Oh, and for me it has never happened by just switching in/out the Zerth katana.

Thanks - the Robe was the problem. I swapped in armor for a fight vs. some magic-immune MOBs. I duplicated the effect this morning. All spells 1-4 unmemorized.

Now I know what not to do.

Things that give you bonus spells, when switched out, can destroy your memorized spells. However, it only happens if you've got empty slots on that spell level. So, when you've cast a spell, leave it in the memorized spells even though it's greyed/shadowed/whatever the heck you want to call how they differentiate them. If you need to rearrange them so that you don't lose a spell you can still cast (at the end of the order) when switching out such an item, remember to replace the one you erase with something (doesn't matter what since it's going bye-bye anyway), even though it'll be greyed/whatever; it makes a difference.

Demodocus, I've sometimes been lucky if I first take off the Improved Robe of Archmagi and place in inventory, and then add the armor. Or vice versa if changing back to the Archmagi robe, first take off armor, then add the Archmagi's Robe. But needless to say I always quicksave first, and will now always be prepared to wait until rest before I can confidently switch the Robe in or out. IIRC, my spells aren't lost as frequently when I take the Robe off.

FelinoidI think this specific problem is a peculiarity associated only with the Improved Archmagi robes of the Upgraded Items mod, since no other items (e.g. D'akon's Zerth or Ring of Wizardry) when switched in/out have erased my readied spells. But maybe I've avoided the problem you mentioned because I've just been lucky to always have my spell picks full (which may be a fortunate by-product of a few games with mage-heavy parties and a neurotic tendency to quickly page down through the book for each caster).