[Serusers] fr_inv_timer + avp not working under high load

[Marcus Hunger]

Hi list,
I am trying to realise dynamic invite-timeout-timers loading timer-settings 
per call from my database using avp. It seems to work perfectly on my 
development-system but fails nearly completly in my high loaded 
life-environment. According to my logs, timer values are set correctly (eg.: 
reply_received: FR_INV_TIMER = 15, see modules/tm/t_reply.c:1371), but most 
of the times the timers have no effect.

My setup is similar to 
http://siprouter.onsip.org/doc/gettingstarted/ch09.html, but avps are not 
written by hand, but acquired with:
modparam("tm", "fr_inv_timer_avp", "mytimer");
avp_db_load("$ruri/username","s:mytimer");

'mytimer' is an attribute in an usr_preferences-table.

Ser's version is 0.9.6.

I already searched the list-archives without finding anything regarding this 
issue. I Also failed accessing the bug-tracker (http://bugs.sip-router.org/), 
it gave me an internal server error. 

Has anybody experienced this effect? Is this a bug? Is there a workaround?

Best regards, 
Marcus Hunger