KiCAD Schematic symbol error

[Lakshmi]

Hi
I’m using KiCAD KiCAD 5.1.6 Stable version.
Recently have created a symbol and added in schematic pages and went back modified symbol and when I updated in schematic , symbol is lost in sch with question mark.

[davidsrsb]

This happens when the symbol library is not in the project library preferences

[Rene_Poschl]

And if you did not take care about the cache and rescue process (libs missing is necessary for this to happen but not enough on its own)

• What are the cache and rescue libs and how does the schematic rescue dialog work? (KiCad version 5.x and earlier)