Thermostat setting issue

I have just installed HKB to control 8 thermostats, 4 of them being Nuheat floor mats and 4 being Nest electric heater controllers.
I use both the Nest and Nuheat plugins and through Indigo, both plugins operate perfectly for all 8 thermostats.

However, when I try to control them via the Home app through HKB, it all falls apart.
The first issue is the Nuheats. No matter what I do, or how I set them in HKB, they always revert themselves to be in Auto mode (heat and cool). If I set the mode to Heat and set a temp, it gets overwritten within a short time and reverts back to a temp range in auto mode.
Also, the temp settings in the Home app are different from the Nuheat app. The latter has the correct values.

The second issue is using the Home app's scene to set all the thermostats.
I have 2 scenes - "heating on "and "heating off". No prize for guessing what they are supposed to do.
Heating on, sets all the thermostats to 65 degrees except the Living Room Nest and Master Bathroom Nuheat, which get set to 73 and 74 degrees respectively.
Heating Off sets all thermostats to 55.
There should be 8 commands to the thermostats, but if you look at the attached log file from Indigo, you can see double writes (1 correct temp and 1 incorrect) to each Nest thermostat in an arbitrary order that results in the wrong setting on some of the thermostats. As before, the Nuheats show the wrong mode and temperature in the Home app but are correct in the Nuheat app.

If I make an Action in Indigo and set the thermostats to be the same as Heating On and Heating off , they both work though it should be noted though that as before, the Nuheat thermostats in the Home app are incorrect whereas the Nuheat app shows the correct values

Any idea why I'm seeing multiple writes to each thermostats and why the Home app doesn't work with Nuheat thermostats?

Minor correction - using the Indigo Action instead doesn't quite work.
I see 2 of the thermostats being set to a different target temperature about 1 minute after the action was executed.
Attached shows a log where I set all thermostats to 55 using the Indigo Action, Heating Off Indigo.
A minute later, it updates the target temp for 2 of the Nests.
Not sure why.

Just a thought - is there any chance the App is overriding what Indigo/HomeKit is trying to do?? I vaguely remember having an issue when first setting up my thermostats.