I'm just a farmer, but this is what I understand about the important difference in 5.10 verses 5.12 software/firmware. (This was an important change, back then)

There is a deal called "The Almanac" that tells the GPS receiver the EXACT placement of EACH satellite (down to the Nanosecond) so it can calculate the ground position. {note: I think, I read , that 8 nanoseconds is about 3 feet down here on Earth}

Now, If you are still using, the OLD 5.10 software, and its Almanac, is 4 nanoseconds OFF [just a guess], because the change "The reference week number got updated to handle the GPS week
     rollover on April 6, 2019" ; then this slightly screws up your ground position, even if it is ever so little. [ BUT it sure screwed up my row shutoffs in the planting season of 2019, and was still on 5.10 software]

The NEW 5.12 software/firmware should have the CORRECT position and "The Almanac" that is current, for satellite placement and reference, in the sky and for our GPS receivers to download.

Here's a copy and paste, of release notes, back then.

.

.

____________________________________________       (copy and paste      )

--------------------------------------------------------------------
                 EZ-Guide 500 v5.12 Release Notes
                   Copyright Trimble Inc, 2018
----------------------------------------------------------------------

----------------------------------------------------------------------
                      WHAT IS NEW IN THIS VERSION?
----------------------------------------------------------------------

Version 5.12
October 24, 2018

Changes since v5.10
Problems Addressed: 
   - Fixes an issue with EGNOS not working on EZ-Guide 500 after a
     constellation change on August 30, 2018
   - The reference week number got updated to handle the GPS week
     rollover on April 6, 2019
   - EGNOS 123 and EGNOS 136 are now displayed on the WAAS/EGNOS
     Satellite Health edit screen instead of EGNOS 120 and EGNOS 124
   - New language packs were generated for the 5.12.003.4 build due
     to string changes

----------------------------------------------------------------------
                        UPGRADE RECOMMENDATIONS
----------------------------------------------------------------------
All users should upgrade.