Workflow Log and Details empty

Dear all,

we're facing a problem and are beeing not able to solve it.

I also attached 3 jpg, hope they'll help to show the issue.

So, in some workflows the workflow log completely empty. There are neither task nor details show. Please have a look on attachement "1.png".

This is the first issue.

After pressing "Refresh" the "Workflow and task" appear (see "2.png"). Okay so far.

But now the user want to see the details of a task. Therfore he may click on the "details button" behind the task description (see 3.png). And nothing will be shown in the details window below.

This error appears now and then. In addition the user has all necessary rights. In case of such faulty workflow no user is able to see the details, not even a with sapall rights. But for some reasons, this error appears. We don't know how to determine the error.

I would be grateful if someone could help!

BR
Mathias