Back I the day I left protools and headed over to cubase because you could play them along with audio in time . Sadly despite years going by and more cores etc its gotten a lot worse. In order to record synth plugins with any decent timing accuracy the only solution is to use a 2nd computer and record the audio. I assume I should be following up with Steinberg and not juce. I assume the audio is on a higher priority thread or something . Sorry to moan I havent had enough coffee this morning .