Good morning gorrit,
Based on the nature of the updates in version 2.5 (i.e., none of them are database-related; you can see the diffs here and here), my hunch is that there might be something non-Clef-related that is causing the error.
Do you mean that immediately after you updated the Clef 2FA plugin from version 2.4 to 2.5, you received a database error message? If so, can you send an email to [email protected] with the following info:
1. What is the URL in question?
2. What is the error message you are seeing? (Include a screenshot if possible.)
3. Were you making any other changes at the same time such as updating WP core, plugins, or themes?
4. What is the hosting setup for this site? Are you on a shared hosting plan, VPS, etc.? Have you experienced any issues with maxing out server resources on this site under load (e.g., running out of RAM or CPU)?