edit contact with ref to address causes fatal error
John guided me to the solution: civicrm is located in Belgium where adresses should be "street number bus" and second line "postalcode city". I used the civicrm (alpha) extension "org.civicoop.streetformatnl" v1.0 to edit civicrm views. Unfortunately it is no longer compatible. If disabled, everything works fine.

Kind regards, Johan.