In the mean time something came to my mind: I have two other lsws installations (one std, one ent). The problem did not happen on those two. They are all configured about the same, except one setting: I/O Event Dispatcher is set to "best" for the servers which do not show the problem and it was set to "devpoll" on the server with the problem. Is there any connection between the dispatcher and this problem? I have now set the dispatcher to "best" on the server with the problem too and will see if this changes anything.