I am using the default one. Apparently it is a common problem with LG G4 but the resolution given by LG is to update the LG Keyboard through settings->general->about phone->update center->app update but there is no update center there on a Verizon version?? I am at a loss??
You can try going to the App Manager and scrolling to ALL then scroll to LG Keyboard and clear the cache. If the keyboard is at issue, which may be the case, try downloading Google Keyboard and set it up as default. If that doesn't cure the issue it's something else. Hopefully not the hardware.