v4.2.1 / v4.3.0 Nextion field mapping?

[G7OMN]

I have a 4.3" Nextion screen, with the ON7LDS driver loaded as per https://github.com/on7lds/NextionDriverInstaller.
Hardware is Pi3B+ and MMDVD HS Dual HAT
The nextion is connected on /dev/ttyUSB0
/dev/ttyNextionDriver is selected
Nextion Layout is ON7LDS L3 HS
Nextion has model 10 v1.05 Build 230820-01 loaded (PD0DIB)
Nextion driver is 1.25

I've recently noticed a change in behaviour on the mapped fields that are displayed in 4.2.1 which is an upgrade from earlier versions, where the current active callsign is being populated in a field that should be the TG description on the other timeslot.
The same symptom exists in 4.3.0 (I tried a clean install of that today, without running the driver install as above - as i know the driver is now supposed to be installed by default.)
I've reverted back to in image of 4.1.6, that i had kept and confirm that it still worked as expected.
Referring to the attached images:
In 4.1.6 with the nextion driver installed via the script:
The idle screen populates the CPU load, CPU cycles and Disk free fields. [416_ON7LDS_idle.jpg]
The TG description field is displayed in the bottom right of the display for each slot. [416_ON7LDS_inuse2.jpg]

4.2.1 & 4.3.0
The current callsign in 1 time slot is now being displayed where TG description should be in time slot 2 and vice versa. - [421_430_inuse2.jpg]

4.3.0
the CPU load, CPU cycles and Disk free fields are not displayed in the idle screen - i suspect this is something the NextionDriverInstaller script populates, as it also inserts extra fields in the MMDVM Host section of config as that section is not present in the 4.3.0 install.

So i'm not sure where this has gone awry - but it looks like it might be a field mapping somewhere, that has been introduced as part of the upgrades against the t8/t9 mappings defined in https://github.com/PD0DIB/Nextion_HAM-r ... %20use.txt

Is there something i should be checking, that i have missed?
Should the default driver populate the CPU load, CPU cycles and Disk free fields? (PD0DIB fields t21, t22, t23)