iTunes not showing correct Contacts (Address) groups when iPad-syncing

[macstatic]

I just noticed when syncing my (iOS 13.5.1) iPad (connected via a USB cable) to iTunes (12.8.2.3) on my Mac (MacOS 10.13.6) that not all my Contacts groups didn't show up (in the Info section).
I've tried adding new groups within the Contacts app, but this change isn't reflected in iTunes.

What can be the cause of this? Is there anything I can reset or check?
And where are the Contacts files located on my mac anyway?

 

[macstatic]

I've investigated further and tried a couple of things.....

1) Created a new iTunes library, then attached the iPad (USB cable) to the Mac. Unfortunately the same Contact groups were shown in iTunes.
When you click on the "Info" section on the left hand side (as shown in this screenshot) you get the Contacts on the right hand side (also in the screenshot below). This list doesn't match what I see in the Contacts app.

2) Fixed a possibly corrupt iTunes database following these instructions. First taking a backup of course (as instructed in that link). Still no change in iTunes when the iPad is attached.

3) Using the exported backup file from iTunes I imported this into iTunes on a completely separate "test" user account on my Mac. Then I opened iTunes (within the same user account), attached the iPad but the result was the same.

4) I've also tried to "Replace information on this iPad" for the Contacts when syncing iTunes to the iPad but this didn't solve my issue either.

From all of this I conclude that the problem lies within the iPad itself, and not iTunes or Contacts, but I'm not ruling that out -so if someone knows of a possible cause, please do tell!
In the meantime I think i'm going to ask in one of the iPad/iOS related forum sections.

 

[macstatic]

I'm stumped!
I've tried all sorts of things, on the iPad (and yet another iPad) as well as the Mac but can't figure this out. iTunes should shown the same Contacts groups and Calendar calendars as on the Mac, but in my case they don't.

I did manage to (mostly) solve the Calendar issue as the iPad allows me to delete them from there, and a new sync reflects this in iTunes, but sometimes the old (long gone from the Mac's Calendar app) calendars still pop up. I haven't yet determined if when this happens -if it's when I sync "All calendars" or something else.

As for the Contact groups I'm stuck and can't change them.
What's even stranger is that I've updated a couple of addresses (in the Mac's Contacts app) but these changes aren't updated on the iPad after a sync.

I have a feeling there's a cache somewhere which needs to be flushed, but I don't know much about how all this works -how iTunes, Contacts and Calendar on the Mac is connected together with the iPad and so on. Perhaps someone reading might have more info on this....

 

[stylinexpat]

I also can’t seem to find option to choose which to use when syncing iPhone or iPad with MacBook. Say you added a new contact on computer and added a new contact on iPhone or iPad then synced. One seems to get lost in this case. Is there a bug in syncing ? No way to choose?