Murena contacts app problems

I was using a private nextcloud but had a server failure.
I have a vcf file of my contacts that I exported from my laptop Thunderbird. If I upload it, I get lots of errors. However, when I load it back into Thunderbird, it’s fine.
Also, when I uploaded it, Murena created the Webmail list. That doesn’t seem to synchronise with my laptop Thunderbird and it duplicates on my phone so that I have two entries for each contact.
Could someone please explain how to replace add my contacts so that they are complete and synchronise across my devices. I am using the native contacts and message apps on my phone, but use the Proton app for emails.
I’m running /e/os on my Fairphone 4 and Debian on my laptop.

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Partial fix: I created a blank contacts list in Murena, linked Thunderbird with it then reloaded the vcf file in Thunderbird. It uploaded, but has the same errors. Murena’s Nextcloud seems to reject entries with pictures, which is most of my family and most common contacts.
Still working on it.
I’ve synced it on the phone and it seems to have stripped all the data except phone numbers. Far from ideal.

I’m now pretty sure this was not a problem with Murena Cloud or with /e/os on my phone, but a conflict between how Thunderbird and Nextcloud store and export/import vcard data. My apologies for bothering you all here. However, if you need to backup your contacts, do it directly from your Murena cloud (Contacts settings > three dots by your chosen address book > Download). That way, if you do ever need to restore your contacts on Murena or another Nextcloud setup, they’ll be compatible. It’s a small file even for my contacts which, though I try to keep them pruned, go back a decade, and doing a weekly download should not be too much of a chore.