Safari NSPOSIXErrorDomain:24 when using Ad Blocking

[athurdent]

If I enable Ad Blocking / Ad Tracker Blocking, Safari on macOS 11.2.2 (iOS/iPadOS is fine) throws NSPOSIXErrorDomain:24 after a few hours.
Turning off Ad Blocking, everything is absolutely fine.
Any idea how to debug or why this is happening?

[sy]

Hi @athurdent,

Does this message appear for all websites or just some blocked ones?

[athurdent]

Hi @athurdent,

Does this message appear for all websites or just some blocked ones?

Everything, not even the Favourites appear anymore when pressing the + button for a new tab. Same error.