Issues after changing Host API for User API

I have recently migrated from the Host API to the User API (the Host API was deprecated).

Regardless I could successfully add a few zones through the User API, I’ve experienced some weird issues with others, for example:

Zone: singrietas.com.ar
2022-06-09 - zone was registered at nic.ar
2022-06-13 - tried to add the zone (at 18:46 UTC-3) but it failed with error 1049, Cloudflare says the zone is not registered
2022-06-13 - a few minutes later (at 18:50 UTC-3) tried to add it again, success!

Zone: estreaming.es
I’ve been trying to add it for a few hours without success, Cloudflare saying the zone wasn’t registered but it was. A few hours later I could successfully add it. The weird part is that the WHOIS database doesn’t return any data for the domain yet.

Zone: diariociudadano.cl
Tried to add it during 2022-06-11 and the following two days without success, Cloudflare always saying the zone wasn’t registered but it was. Asked in the community forum and they told me that the domain should be delegated to somewhere in order to be able to add it, but that sounds odd, because I was able to add other zones that weren’t delegated (like pescaregional.com.ar). In the case of diariociudadano.cl I could only add it by delegating it to somewhere first.

Zone: anunciacasa.es
The zone appears to be registered in the year 2019.
The day past yesterday I tried to add it two times at 12:26 (UTC-3) with no success. But a few minutes later (at 12:44 UTC-3) it was successfully added.

I’m not sure if these issues are related to each specific zone or it could be something at Cloudflare end. I would like to understand better what is that Cloudflare checks before accepting the zone, so maybe I can perform some of those checks at my end before trying to add the zone.

What do you think? Thanks!