.sym is not a kicad library file ending. And definitely not a one related to footprints. It might be either a spice symbol file or possibly the exported graphical info of a kicad symbol. (at least in v4 one could export either the full symbol resulting in a lib/dcm pair that can be directly used or export only graphics as a sym file which can only be imported via the symbol editor and must then be stored to a library to be accessible to kicad itself) scrap that there is no “.” between “esp32” and “sym” meaning i read it wrong.
New idea: give us the full file path of the files that make problems. possibly show them within the file browser.
And you might want to read: Library management in KiCad version 5
By the way you can drag and drop one image per post (as a new user) which will result in it being shown inline.