Cubase MIDI out (latency) issue, please help!


I’am having trouble with sending (MIDI out) commands to my external Korg Z1 synthesizer. Sending the commands from my MIDI track causes no problems but the problems occur when i use the controller lanes.

I have configured many controller lanes within Cubase and the synthesizer so i can control most of the effects of my synthesizer from Cubase. This works fine and causes no problems.

If i make small adjustments in the controller lanes then it causes no problems but whenever i make big adjustments, such as, fast curves or use more controller lanes simultaniously then the problems happen.

Some of the commands get received a few seconds later,
Some commands get skipped or effects keeps hanging at a certain level,
The commands don’t get received at all.

Using MIDI in with Cubase, or sending effects from the synthesizer, also causes no problems.
(although i don’t use that quite often)

I used to think that my old and sluggish computer was the problem but now i have a totally new setup
and the same problems remain.

My previous setup:
PC 3.4 GHz
Memory: 2 GB, DDR 2
Audio Interface: Tascam US-122L
Korg Z1 MOSS Synthesizer
Cubase 3

My setup today:
iMac 3.5 GHz i5
Memory: 16 GB, DDR 3
Audio Interface: Steinberg MR816x
2x Korg Z1 MOSS Synthesizer (i recently bought a second one)
Cubase 8 Pro

The problems are just as bad on both computers with both of my synthesizers.

I would love to hear what causes this or what’s “most likely” to be the problem?
Any help or advice is much appreciated.