Resetting iPad/iTunes Mac sync? (Calendar & Contacts sync issue)

[macstatic]

Is there a way to reset the synchronization between Calendar and Contacts on my Mac and an iPad?
My problem is that whenever an iPad (I have two Minis: 1st gen. (iOS 9) and a 5th gen (iOS 14) ) is attached to the Mac (USB to Lightning cable) and I open iTunes (12.8.3.1) on the Mac there's a mismatch between the various calendars in the actual Mac Calendar app and what's shown in iTunes, and similarly with what's shown as contact groups in iTunes compared with the contact groups in the Mac Contacts app.

I believe these are some old entries which for some reason haven't been removed whenever they've been deleted from said apps.
So is there a way I can reset the synchronization so that only the actual entries I have in those apps show up?

 

[macstatic]

UPDATE:

I've tried to sync the iPad (actually both of them) by first deleting all Calendar and Contact entries (deselect the "sync" button for said apps in iTunes on the Mac prior to syncing), synced, then physically disconnecting the USB cable, reconnecting and re-syncing again, only to see the same entries (which aren't supposed to be there) are still present.

Then I've tried to clean up my Mac using Onyx to clean the caches etc. followed by a reboot, and also powering off the iPad, then restarting it again.
But no matter what I do, when any of my iPad are attached to the Mac and I open up iTunes, there are several Calendars and Contact groups shown which aren't present in the Mac Calendar or Contacts apps.
What can I do to solve this problem?

UPDATE 2:
I tried something entirely different after reading this thread concerning a similar problem (alas no solution found though)....
So first I exported my Calendar and Contact app info. Then I transferred it to a new Mac user account (where I had never touched either of the above apps nor iTunes, and not synced my iPads to this account either). In other words: factory fresh setups, but waited to import the data.
I then opened up the Calendar and Contact apps for the first time, and not surprisingly there wasn't any info there to be found, but a couple of new calendars were created in the Calendar app by default: Calendar, Home and Work.
I synced these to the iPad (via iTunes) and all looked fine.

I also tried removing the iPad's calendars a few times, then re-syncing just to be sure, and again all seemed OK.
So next I decided to import the previously exported Calendar and Contacts files from my normal user-account. That too appeared OK, but when syncing to the iPad all of a sudden all those old, long gone calendars (that aren't shown in the Mac Calendar app) popped up again! So I quit iTunes, then deleted the Mac Calendar folder (~/Library/Calendars/) which in theory at least should reset everything (and according to what I could see in the Calendar app itself afterwards, it did indeed remove all my calendars and start from scratch again).
Well, strangely, when restarting iTunes with the iPad attached all those other old calendars which shouldn't be there were shown (and this is after deleting all the calendars on the iPad). I then concluded the problem was with my data within Calendar, and perhaps exporting each calendar one by one as individual files might be the solution, delete the entire calendar folder and import each calendar one by one. But for some reason iTunes still shows all the old calendars. I assume this means the data is no longer fetched from Calendar but from a cache somewhere. Maybe some sync cache or something. Any ideads how this all works and if there are other files I can delete to reset the sync functions?

 

[macstatic]

PROBLEM SOLVED!
Finally, I've found the cause and a solution, thanks to this thread where it's discussed in more detail, but here's a short summary:

a) the cause of the problem lies within the Contacts app (on the Mac) entries. If any contact has the fields "son" or "daughter" then it won't sync with an iPad/iPhone.

b) the solution is to either remove all instance of "son" and "daughter", or replace it with another field (luckily there's a "child" field which is a suitable replacement and works when syncing).

I've made a script available (download or copy/paste from the linked forum post) which checks all your contacts for "son" and "daughter", then replaces any such instances with "child", taking the tedious process of manually looking through them yourself.
Once that's done you can again sync with your iOS device using iTunes.
I hope this proves to be helpful for someone

 

[stylinexpat]

I am still having trouble with sync. The old days iTunes worked great between an iPad, iPhone and MacBook. You just plug in and they all sync between devices but now this seems like something Einstein is required to solve. Such process should be simple and easy where a person opens their computer, opens iTunes, plugs in iPhone to MacBook Pro and iTunes automatically recognizes all new info on computer and iPhone then updates both of them with the latest info from Each device and then when one disconnects and plugs in an iPad device to the computer after it does the same. This should not require a rocket scientist or engineer to do. Not everyone wants to use cloud and upload all their personal info to a cloud server. Apple devices should be able to sync with each other wirelessly or via cable without some external cloud server to sync basic info on devices like Contacts,Calendars,Notes,Photos and Music (just to name a few).