Have you tried a simpler preset, simpler instrument, lke the  harpsichord?

I am using a MacBook Pro 2.6 ghz I7 processor, Apogee Symphony IO + Thunderbridge and Pro Tools 11.
I am experiencing a problem where during monitoring with just having one track of pianoteq I get a CPU overload error which occurs randomly.
At first I thought its related to other plugs on other tracks, but I then instantiated only one interment track on the project and noticed that it is clearly a pianoteq issue. When replacing this with sway an Ivory II plug I never get this error.

I am using 64 buffer size, under 48khz sample rate

Note that under logic X I never get this error with the pianoteq, with the same sample rate and same buffer size.