Issue View shows fields of second tab when first opened

We have an issue type with two tabs (General, Reopen).

The field "Reference" should be on the General tab, the fields "Last Assigned Date" and "Reopening Counter" on the Reopen tab.

When this issue is opened, the General tab is selected and we see all 3 fields on the screen (one from the General tab, and the two from the Reopen tab). See "Issue first opened.jpg"

Then select the Reopen tab: We only see the the two fields of this tab. That's OK, see "Issue Reopen Tab.jpg"

Then back to the General tab: We only see only one field. That's OK, see "Issue back to genral tab.jpg",

So, the Issue shows only the wrong fields when opened first.