Strange behaviour with password secured PDF

DTPO 2.8.1 on OSX 10.9.5
in my DB there is a PDF which is secured by a password. When I click this doc in the 3-fold view (with cover flow activated) anything in the DTPO window disappears (except the navigation sidebar). Normal behaviour when clicking on a secured PDF should be to be prompted for the password in the preview window.

I already tried DB repair, restart of DTPO unsuccessfully. Once after a restart of the Mac I was able to recover normal view and was able to reproduce the erraneous behaviour. Currently I´m not able to restore normal view.
I recorded a screencast but upload is not possible here.
The same (replicated) DB on a Macbook Pro with DTPO 2.8.1 / OSX 10.7.5 works well.

Rats! I just resized the DTPO window to take a screenshot and now … everything is visible again. However the problem is no longer reproducible.
That is strange…

btw: I recorded a screencast which is 15 MB and .mov format, which is not allowed to upload. Keep it for future use, if needed by the support

Known problem-reported here.