Thanks for the reply.
We have not started manual active fulls and we have no scripts manipulating jobs.
There are VIB files in the directory, but they are all from before 10 March.
I have been trying to compare settings with another veeam server we have, the jobs there run fine without a hitch.
As far as i know there are no global settings for this that might overrule individual job settings.
I looked at backup window settings as well, i thought that might cause issues when the backup would be interrupted and then simply start all over again with the active full on the next schedule time.
But not all jobs with the problem have this setting enabled.