It seems clearly that some of the server parameters that were changed in the newest versions of Kolibri have had a negative impact in your setup.
You said in a previous comment that you tried to do what I suggested at Kolibri v0.10 has been released! without success. I am giving you now the parameters to set in the options.ini file that’s in that directory to have exactly the same setup version <=0.9.1 had.
CHERRYPY_THREAD_POOL = 10
CHERRYPY_SOCKET_TIMEOUT = 10
CHERRYPY_QUEUE_SIZE = -1
CHERRYPY_QUEUE_TIMEOUT = 10
As you said, using this setup everything should work slower, but with so few users will work unless you have a lot of requests. I would like to know why the current setup does not work properly for you. Many tests have been made before fine tuning this parameters to avoid this kind of problems.
In any case, please, if possible, try to connect always the server to the router using a cable, not wifi. Wifi is fine for the clients (that explains why you have a decent speed browsing Internet), but not for the server that supports most of the traffic.
Please, give us some feedback on the results of this change.