Jopie

Good day
I accidently figured out what to do the get the batteries charged.......
Turns out USB setting must be used on the MAX inverters. USB setting on the MAX is the same thing as SUB on the VMiii.
2 nights ago I switched over from battery mode (SBU) to utility (SUB) as I planned to use the aircon and don't want it running from the batteries. I accidently put it on USB instead of SUB. The next morning it charged the battery as "first priority". 
The MAX is perfect, just a little feeding back to the grid, but I can live with that.
Overall I'm very happy now

Good day
I accidently figured out what to do the get the batteries charged.......
Turns out USB setting must be used on the MAX inverters. USB setting on the MAX is the same thing as SUB on the VMiii.
2 nights ago I switched over from battery mode (SBU) to utility (SUB) as I planned to use the aircon and don't want it running from the batteries. I accidently put it on USB instead of SUB. The next morning it charged the battery as "first priority". 😂
The MAX is perfect, just a little feeding back to the grid, but I can live with that.
Overall I'm very happy now

If you need to charge batteries with solar and utility simultaneously, use option 1 - USB and option 16 - SNU. I just tested it, it works.

Good day
Bad news again with the 7.2kW MAX...
Seems like all 3 versions of software does the same thing, no charging of the batteries in cloudy conditions and it feeds back when the sun comes out...
Below I attached a screenshot, orange is load, green solar, red grid. Around 12:30 the geyser switched off and then it pumped 800W back to the grid, luckily I saw this and switched it back to SBU mode... Same thing just before 16:00, I switched it to SUB and immediately it fed back to the grid, switched back to SBU again...
The bottom graph shows battery charged nicely (SBU mode) until the geyser switched on at 10:00. At about 10:20 I switched it to SUB which worked as it should (red line) until it switched off as per above. But one can also see that no charging happened while the load was more than what the PV could provide.
It's a pity it doesn't read the battery current, that's why "battery watts" and "Current" is zero.
Today is very cloudy again, I'll be brave and leave it on SUB for the next 24 hours and have a look at those graphs again 😒

Good day
I managed to flash 12.13 and 90.28 just now... I was very happy at first to see that it charged the battery in SUB mode, until the AC kicked on again... Then it draws 0.5A
I'll see if it feeds back to the grid tomorrow and report back... But at this moment it seems like the same problem still exists... No charging of the batteries in SUB mode no matter what charge settings are used if there is insufficient solar power...
Tomorrow my new batteries arrive then I'll have 16x 105Ah deep cycles, should be enough to just keep it in SBU mode permanently... It's just those cloudy days that worries me a bit... I usually would put it on SUB mode before I leave for work on the old VMiii, then I knew my batteries would be fully charged and access solar would not be wasted.
Thanks for all your help @Dirkie and @Coulomb
PS Still no feedback from supplier wrt their firmware yet, I'll post here if they send it😀