I have problem with completion window location when vertical scroll of SyntaxEditor is not at start position. In that case position of completion window is at the top of control, in same case, somewhere else. I reproduced such behavior on minimal example which I am sharing with you right now.
As you can see in the images, in the first two cases everything is ok, but in the third image, when the vertical scroll is not at the start position (moved a little bit), the completion window has a completely wrong place.
Thank you for your answers.