Contacts didn't restore SE to 6s

Ok, so with extensive help from AppleCare support supervisor (I got bumped up from support because the problem was so weird), we determined it wasn't the phone.

A *lot* of weird things were going on (including the vanishing of those contacts I needed on the SE), too complex to type here. For some reason, the missing contacts seemed to be associated with a Microsoft Exchange email, and for some still undetermined reason, they weren't coming over from the SE.

What ultimately saved me was a previous back up of my SE on the Mac app, iMazing, which lets you dig into individual categories of the back up (Messages, Photos, Contacts, Voicemails, etc). From that back up, I was able to export my missing Exchange contacts as vCards, then I could import those vCards into Contacts on my iCloud.com login. I made sure my iCloud Contacts sync was on, and BAM, they appeared on my phone.

A couple things about this. 1) my iTunes & the iMazing apps on my Mac were set to sync over wifi when the app is launched and the phone is plugged in. In this rare instance, that was a mistake because when I did that, the back up of my now missing contacts on my SE overtook the backup that had those contacts (iTunes). Same thing happened on iMazing.

BUT, I had a previous back up on iMazing listed that I could tap into, and that's what saved me.

2) I've seen several folks on the community here say that contacts aren't stored on the phone, but the AppleCare supervisor said that the phone does store them when they're synced from the email addresses. That is also shown to be true because the older iMazing back up had them available, and any full back up app will take everything that's on the phone to create the back up (with, I guess, the exceptions that Apple lists). Just an FYI.

Thanks. I've seen this reply before in other threads. I have different contacts in different email addresses. I have compared the settings of the SE with the 6s and they are identical. Contacts > Groups have all the same addresses & check marks. Settings > Contacts have all the same information. iCloud > Contacts are enabled on both.

So, why hasn't all the information transferred is the question at hand? What am I missing?

Also, I don't understand why manually entered contacts haven't come over and why some phone numbers are there but the contact names aren't.

Actually, I'm mistaken. My Yahoo account is listed in Contacts > Groups on the SE but not on the 6s. However, I'm logged into the Yahoo account on the Mail App, and Mail App's default account is that Yahoo email. I don't get it why it's not showing up in Contacts > Groups.

Under Settings > Passwords & Accounts, that Yahoo addy is listed and "contacts" is on. I tried turning it off then back on again with no luck.

By the way, my wife and daughter recently went through this phone restore from iTunes from old phone to new, and they said they had no issues and no fiddling about to get their phones to match.