Do not know source of error
 

I cannot figure out which addon or lib is related to the error I am getting.

Is it happening when you find books? That'd imply it's an addon doing something with books. Such as the one saying "Book added to librarian"

If that's not the case, then just disable a large chunk of your addons and see if it stops happening, then slowly enable/disable more.

It is happening when I interact with lore books but also quest items. That is a quest item in that SS.

Yes it is happening with anything that is a book. I have no dependencies for my addons. I guess I will have to search for the offending addon the old fashion way and turn them all off and back on again one at a time since nothing in that SS indicates what is causing the issue. ugh

I have turned off all addons that seem to relate to books plus more and the error still persists. I have never before seen an error that did not indicate what the offending addon was.

Does it still happen when you disable ALL addons? If so, it's not related to addons, but a bug in the game itself.
Otherwise I suggest you install LibDebugLogger if you don't have it yet. After you have it installed and got the error, log out of your character, go to your Saved Variables folder and upload the LibDebugLogger.lua somewhere, so you can share it here. That might give a clue why this error is happening.

Thank you. It does not happen with all addons disabled. I will try the try the debug logger when I get back home.

Edit: I turned off everything. Made sure there were no issues. Turned on some basic addons and the related Libs and still no issue. So far I have turned on everything I think I need and I am not getting the error.

Did you find a fix for this problem as I now have it. I have tracked it down to the Librarian Book Manager addon as when I disable it the problem goes away. There are no dependecy issues with the addon so not sure what's causing it.