I tried create a new user with new openbox config and the error persist
This post may help you
Sorry if I would, it would be useful to post the bug, to the compton maintainer so that I can fix the bug.
I hope I have not offended anyone.
Thank you to show where are the problem, i just install compton-git and it works fine now.
Please mark it as solve as it s ok now, glad that you got it fixed.