Problem with external Synth when connected with USB

I have problems with all my external Synths when I connect them via USB to my macbook Pro and open Logic Pro X. Then they start to oscillate in a high pitch as if it would hold down a very high note. It will play the midi notes that I am sending out, but as soon as it is not sending a note, the high pitch returns. I tested it with several synths and I only have the problem when I am in Logic. It is not happening in Ableton. So it should be a Logic Problem. Midi Monitor is showing me a lot of sysEx messaging is going on, but I don´t know what that means. Anybody has a solve for this?

i am not using an usb hub or midi Interface