Seems we are rendering the false-colour scene used for picking on the display on mouse-press which seems really sub-optimal to me =) We should fix that.
Jan Holesovsky committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/core/commit/?id=fdace2238a262c88562f3461feae45dec75cd02c fdo#83717: Fix the bar picking in the 3D charts. The patch should be included in the daily builds available at http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: http://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.
Fixed now, both in normal and benchmark mode.