Cubase 7.5 Pitch Bug?

I have an Intel i7, 16Gb RAM, Win 7, Cubase 7.5, using about 120Gb of a 500Gb solid state main drive.

When I am editing an instrument or midi track, sometimes the instrument pitch will drop by a half step. Everywhere I look, the parameters are still correct, but the pitch has lowered such that if I or midi plays the E key for example, the note heard is E flat. The rest of Cubase plays the correct pitch, i.e. the audio tracks (of course), and the other instrument tracks.

I have had this issue for a while (I think even with Cubase 7.0 and 6.5), but it seems to be getting worse. I thought it was in HALion, but now I have Komplete 11 Ultimate and it is doing it with those instruments as well. My keyboard is just a controller, no sounds, and it does it with the virtual keyboard as well.

The only way I have found to make the pitch correct again is to close/reopen Cubase or change the instrument, e.g. change Kontakt to Massive, and back to Kontakt. If I tune the instrument up a half step, it works, but will be wrong when I reopen Cubase.

Could it be as simple as getting more RAM? Performance has slowed since I started using Komplete 11 and Izotope 7 and it seems like it only happens during more intensive tasks like editing an instrument or midi track.

Any help is appreciated as it is getting more frequent and annoying.