Before trying any fixes, verify that your device is actually in EDL (Emergency Download) mode.
Not all QFIL builds are equal. Older QFIL versions (from 2016-2018) have buggy serial handling. Newer phones require QFIL from the (version 2.0.2.2 or later). qfil failed to open com port handle
: Unreliable USB cables or ports can cause intermittent connection drops that trigger the handle error. Before trying any fixes, verify that your device