For those interested, the latest BIOS (1.13.3) does resolve the issue for me. Thanks Dell. Fixes:- Fixed the issue where the system does not turn on when you connect a USB-C monitor with Dell Power Button Sync (DPBS) feature.- Fixed the issue where the BIOS recovery using hard drive fails after updating the BIOS to version 1.9.1.- Fixed the issue where the system prompts for a password after rebooting the system when Reboot Bypass is enabled in BIOS Setup menu.
I have a bunch of new Latitude 3420s that all have these problems when doing a PXE boot. low-resolution-in-preboot-environment-winpe-boot-image  progress-bar-is-invisible-in-pxe-boot  This is clearly a firmware issue but updating them to the current BIOS version HAS NOT fixed it. Has anybody else seen this?  Dell, are you planning to fix this or not?  I need an answer.
Latitude 3420 Low Resolution in PXE boot and WinPE