I have just upgraded to Logic Pro X 10.4.8 and I am experiencing playback problems with existing scores which were not previously problematic. Some instruments are sounding on after they should cease sounding. Sometimes this happens and sometimes not, with the same file. I have to cross my fingers when creating WAV's hoping to get lucky. ALSO one of the Studio Horns trumpet parts is ducking down in volume suddenly. I have searched everywhere in the file for a solution.