Font Trebuchet italic "ä" shows as non-italic.

In LibreOffice ( Calc and Writer, the italic “ä” shows as non-italic, when using Trebuchet font and copy-pasteing text from a filename in Finder (OSX 10.10). The issue remains even if I paste the text unformatted. If I type the same text manually, there is no issue.

Funny detail: If I press backspace at the “ä” to remove it, it first turns into “a”, after which the italic DOES work. Could it be that LibreOffice is registering the single letter as separate a and ¨? Although, if I type ¨ and a to create the “ä”, the italic DOES work correctly.

OpenOffice does NOT have this issue in Writer or Calc.

Anything I can do to pinpoint the issue? Or perhaps fix the issue locally?