Inbox Mailpreview corrupted

Few of our Notes 8.5.2 Users reclaim us following situation, seems like an Error in the Mask of the Inbox of the Standard Notes Client:

When they have activated the Messagepreview, the Header is not visible. Notes doesnt show anything, like the “From” Field or “Subject” Field or the CC Field.

But when the User open the Mail manually the Header is visible.

We cannot find any solution, so please help to fix this Bug.

We also have the actual Fixpack installed, most Users also run on Fixpack 2 +.

Do anyone know this “bug”? thanks