[SR-Users] Sintax errors can stop the machine?

We are facing a periodically problem with a server that is running Kamailio 1.5.2. I think that it is not the case, but I will ask anyway. Some clients, sometimes, send us messages with sintax errors. This machine needs to be rebooted every week. It stops working completely. I don't think that SIP messages with this kind of errors can lead the machine to its 'death'. This proxy is very simple: it just receives and forwards the calls to pstn carriers. The routing rules are defined in the script, so we dont use modules to take the IPs and all other information about the carriers. The database is used just for ACC. Nothing more. Also, it is not receiving a flood atack. We have several servers running at this time with a huge number of clients and we never had this problem. This machine is the only one that does not want to work without a weekly break :) The causes, in my opnion, will be with the operational system or something physical. But, I would like to know if somebody already saw this behavior with SIP messages. tks a lot bruno machado