eldonb46 wrote:- Install and Check for the current "~/.arduino/packages/esp8266/hardware/esp8266/<file>", which is installed via IDE Tools -> Board: -> Boards Manager...
As some other people faced, don't really blindly at the BoardManager if doing upgrades. Sometimes (or probably all the time), it won't uninstall previous versions, and in the path mentioned above, you can end up with several versions. Simply delete old ones.