Cubase MIDI out (controller lane) issue

The main problem i’am having is that my synthesizer doesn’t receive commands correctly or skips commands.
(excuse my english or the fact this might be a noob question :smiley: )

The more commands i send from my computer to my synthesizer, the less commands get received by my synthesizer.

My synthesizer has no problem playing a (MIDI out) melody send from cubase.
Most of the time i use “controller lanes” and this causes problems.
Slow changes in the controller lanes causes no problems but whenever i make short changes (short curves) or use more controller lanes simultaniously then my synthesizer skips certain parts.

I used to think my ancient computer was the cause but my new Mac with 16g memory has the exact same problem.

What am i doing wrong?

Please help!