Here are a number of issues I observed when powering the Wireless Tracker with USB-C and no battery.

• After "turning off screen" is logged, VEXT drops to 1.48V instead of 0V.
  I haven't measured VEXT with a battery attached.

• Once the screen is blanked/off, VEXT periodically cycles between 1.48V and 3.3V.
  The UC6580 will stop transmitting NMEA sentences on GNSS_TX and has maybe browned out at 1.48V.
  The 3.3V supply never drops out.

• After 10+ seconds (10-30s?), VEXT returns to 3.3V while the screen remains blanked/off.
  The UC6580 emits its product info "boot" message and begins emitting all the default sentences.

• The brown out / reset results in all of the NMEA message output configuration settings ($CFGMSG) being lost so there is a verbose stream of sentences being transmitted.

• According to the manual, V_BACK will maintain RTC, almanac, and ephemeris data but not other settings.

Again, I have only observed this when powering the Tracker solely with USB-C.

Perhaps it's a board design issue and/or the expectation is that there is always a battery or a VDD_5V supply?

Of less importance:

• According to the Unicore Firebird II Protocol Specification doc, a $CFGSYS,hXXXXX implicitly resets the UC6580 GNSS module and any other prior settings will be lost and would be need to replayed.
  You can try this and you will see the boot info replayed.

• The "enable everything" $CFGSYS,h35155 command is likely unnecessary as the module defaults to this configuration and the default enables all possible constellations.
  This can be confirmed by a $CFGSYS query.

Of even less importance:

• The on-screen GPS count appears to be "latched" to the last successful fix.
  If GPS lock is lost then the display still shows the count of the last fix ($GNGGA).
  This might be by design? I'd still like to know if I have lock or not.
  This observation might be a result of the UC6580 resetting and not the norm.