Portamento in ST2.5 broken?

[brotherone]

Hi!

It seems, that the portamento in ST2.5 is only working in a limited note range.
If I play in legato mode e.g. C1 as the lowest and than subsequently the notes from C4 to C5 while holding down C1, then ST is only playing notes up to Fis4. From G4 on to C5, only Fis4 is played.
In mono mode, erverything is working fine and all notes are played correctly.
Can someone reproduce this issue?
This happens in stand alone mode and in Reaper.

Best regards

P.S.: is it possible to upload Mp3's in this forum, this would make it easier to explain???