Ubuntu - mouse problem - location and rightClick()

Hi,
I'm using sikulix API (Java) to run automated GUI tests on a jenkins machine running Ubuntu. Everything works great apart from one thing:
I want to right click on a file in the eclipse project explorer and hover/click on the context menu that should popup. I want to to this with the rightclick-function using a match object "m" and a Screen object s.

some code:
m = m.right().find("test***Generation/com_******_.png"); //Find the file
m.rightClick(); //Right click on it.
m = s.wait("test***Generation/******.png", 3); //Wait for the context menu to show up

This works fine on windows but refuses to work on Ubuntu. Now to the weird part, sikuli finds the picture and hovers to it. It seems to invoke some kind of click on it because it is marked but the context menu refuses to show up . Something I have noticed when running sikuli in Ubuntu is that the cursor does not always follow the click/hover, i.e when I'm clicking on things it is an "invisible cursor". When the tests are done and I'm touching the mouse the cursors always moves to a complete different place on the screen. The location that the cursor moves to when I'm touching the mouse is not right-clickable.

Another weird thing is when I only run the three lines of code mentioned above rightClick() works but there is still an "invisible cursor" doing the job. It is not working when I'm running the complete test suite, I'm only using functions from the sikuli API to move the mouse.

I'm sry that I can't post all code, Im currently working for a company developing GUI tests for their in house eclipse plugin (therefore the "*" in image path) and can't leave out to much information.

I know it might be very hard to reproduce/debug this but I thought that you might have some ideas of what could be the problem or give some tips on how to debug this. Please let me know if you need more information and I'll do my best.

Thanks for a great tool,
BR Jonas