MIDI timing problems with Logic Pro X

Since upgrading to Logic Pro X, I'm frequently encountering problems with MIDI timing, using virtual synths such as EXS 24, Battery, and Ultrabeat.

During a busy arrangement, adding simple patterns such as a high-hat doing 16s or 8s on the off beat, timing can become sloppy and subtlely un-tight.

Even bouncing to audio still exhibits the problem, when zooming right in and attempting to "tighten up" the audio by manually quantizing it as desired.

Despite other issues, this was never a problem in version 9. It's a particular issue when using custom groove quantise templates, but still occurs even with standard "out of the box" quantise settings.

I don't think it's my sound card, as the problem still occurs when using the built in output on my Macbook Air.

I've also tried various different latency settings to no avail.

I'm running OS X 10.10.5 and Logic Pro X 10.2, but it's been happening on all versions of Yosemite and Logic X.

Has anyone else experienced similar? Any tips/advice for other things to change into order to eliminate this?

Many thanks in advance for any comments/suggestions.

If need be I can post an audio clip to demonstrate, though it's a subtle slackness which may not be immediately obvious on listening.

FZ