I solved the issue with a combination of measures:
-
mark all active messages that have been submitted but not sent properly as sent.
-
in phpadmin make a change to the database.
2.1. select phplist_sendprocess and delete all lines that show up. -
make the change in line 1326 of actions/processqueue.php ( Avoid possible divide by zero when calculating message send rate #925 ), as suggested above by Duncan.
-
in admin/connect.php replace
%0.10f
by
%0.10F
as suggested in #2 of Campaign stops after 1 email if language is not englisch