[gloriousglib]

Thanks! Certainly deleting temp is much quicker lol. Here's the entry from the crash:

./luajit: frontend/apps/filemanager/filemanagersearch.lua:323: attempt to concatenate a nil value
stack traceback:
	frontend/apps/filemanager/filemanagersearch.lua:323: in function 'find'
	frontend/apps/filemanager/filemanagersearch.lua:227: in function 'close'
	frontend/apps/filemanager/filemanagersearch.lua:198: in function 'callback'
	frontend/ui/widget/button.lua:154: in function 'action'
	frontend/ui/uimanager.lua:270: in function 'checkTasks'
	frontend/ui/uimanager.lua:296: in function 'run'
	./reader.lua:207: in main chunk
	[C]: in function 'dofile'
	./koreader-base:22: in main chunk
	[C]: at 0x0000bd85

Originally Posted by WS64

@gloriousglib, instead of reinstalling Koreader delete the temp folder within Koreader, or, and that might be the even better idea, sync the reader again with Calibre.
This temp folder and its content, a file called metadata.koreader, will be rebuild after the first search.
I wonder if your metadata.koreader file contains something "unexpected" that I should prevent, but since it is unexpected I don't know what to search for.

So when it crashes check the file crash.log and post its content.
And check the also the content of this metadata.koreader file, there should be a path to each book, is this really where the books are? In case you either moved that file or manually deleted books without Calibre being involved the search should lead to "file does not exist" (btw, it should actually tell you the complete filename and path which does not exist, another way to check if the data are correct), but in no case Koreader shpuld of course crash because of that.