I'm wanting to transfer a domain from https://www.discountdomains.co.nz/ to https://metaname.net/
It is used just for email hosted at a third company - https://www.hostinger.com/
I set the TTL for all records to 5mins, thinking that would help, then I followed these steps to the letter: https://metaname.net/my/transfer_help
Which are to create the zone at Metaname

, then set the nameservers at the current registrar to Metaname's nameservers.

Wait till five mins past the next hour, then transfer the domain for no downtime.
Except I haven't wanted to do the transfer, because twice now I've tried this, and I get stuck with email sent to my user being bounced, till I return to using Discount Domain's nameservers and zone record.
I tried this yesterday, and experienced a two hour interruption in service before giving up. I tried again today, and am now five hours into a service interruption.
I emailed Metaname support yesterday after I aborted the first attempt, and they just replied that I should be sure "Names that are fully-qualified such as www.vivacissimo.net.nz. or ghs.google.com. should have a trailing dot". Yep - they are. And I also showed them they were in a screenshot.
I then emailed Hostinger and had them look over everything I'd set. They replied that it all looked fine.
I'm stumped and increasingly frustrated. I don't want to proceed with the transfer, because I don't know what's wrong. I only know that yesterday it was fixed by returning to the prior setup in Discount Domains using their own nameservers and own zone record.
TIA for any advice you might have :-)