In a recent Newsletter of mine, some (not all) users could not open any links. Klicking on a link only poroduced an error message that began as follows:

Illegal mix of collations (utf8mb4_general_ci,COERCIBLE) and (utf8_general_ci,IMPLICIT) for operation 'regexp' ...

I can send the full eror message in a private mail if that helps.

Any idea what this could be?

Thank you in advance for your help.

Matthias