Since Ventura, the Mail app sends emails twice

Since the Ventura upgrade, the Mail app sends emails twice, but it's not all emails, and I can't figure out why.

What I see is that some emails get stuck in the Outbox, even though they left properly. As a result, they get sent a second time.

I check existing thread with a similar problem. I tried keeping sent messages on my local machine only, but that didn't help. I removed my email account and then re-created it. It didn't help.

I'm currently with Fastmail and using IMAP in Mail. Any help is greatly appreciated.