Illegal Private Key for Crypto App (NextCloud 16)

Nextcloud version:
Operating system and version: Arch Linux
Apache or nginx version: Nginx mainline 1.15.12-1
PHP version: 7.3.5

The issue you are facing:

Since updating Nextcloud 16.0.0 to I see a light blue banner at the top of the window reading “Ongeldige privésleutel voor de crypto app.(…)” which is Dutch for “Illegal private key for crypto app”.

Under “Settings” -> “Security” -> “Encryption Module” I read “Het wachtwoord van je privésleutel komt niet meer overeen met je inlogwachtwoord.” which is Dutch for “The password of your private key is no longer in accordance with your log-in password”. However, I did not change my password since july 2018, nor do I remember what my password was before that.

Can someone tell me what’s going on here and how to get rid of this banner?

Thanks for any help