Monica doesn't reliably add synced contacts

[Silun]

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github (I've searched it).
• I agree to follow Monica's Code of Conduct.

Bug description

Contacts synced to Monica via CardDAV can fail to be added, they do not even show up in the audit logs at all.

Steps to reproduce

1. Install Monica Version: 4.1.2 via docker
2. Get API token
3. Add Monica to Thunderbird v128.4.0esr via CardDAV
4. Sync contacts into Monica
5. Thunderbird doesn't receive an error, shows all contacts as available in Monica's list, everything seems fine
6. Monica adds about 57 contacts per minute, not more
7. Check audit logs, the contacts after # 57 do not show up at all
8. Wait a minute, sync more contacts in small batches, and get roughly 57 contacts per minute for a total of 113 after 2 minutes

Expected behavior

Monica should either just create all contacts it receives or throw an error, do rate-limiting, whatever, just not fail silently. I am now anxious that it may silently dispose of my contacts without me knowing.

As a sidenote, Monica actually deleted contacts that I remove from the address book via CardDAV. I completely cleaned the list in Thunderbird and synced, and all contact profiles were deleted in Monica. Monica did not ask me or tell me about that, it just straight up deleted them. If I accidentally do a bad sync, Monica will just delete people?

Environment

Your own self-hosted instance (monica v4)

Version of Monica

4.1.2

Installation method

Docker image

Web server

Other

Database engine version

MySQL

Additional info

I just quickly Monica up in docker to test it out, and instantly faced this issue where first it wouldn't sync right, and then also just straight up nuked all my contact profiles. No damage was done, it was just for testing, but damn is there no protection against this?