[Users] Receiving different VIA in INVITE and CANCEL

Hello, I have an issue with some user agents, (Linksys PAP2 and Sipura 3000) sending different Via in CANCEL than in INVITE. Of course the result is that the caller hangs up and the callee keeps ringing. I tried to use modparam("tm", "via1_matching", 0) but it did not solve the problem. I have two questions: 1. Is the via1_matching in TM working as described or is it broken? 2. What can be causing this behavior of the user agent? Not all our users who have these user agents report this problem (actually very few have the problem). In our lab we tried same user agent, same firmware but could never reproduce this behavior no matter how bad we tried to mess up their configuration. Any help will be greatly appreciated. Thanks. George Disclaimer The information in this e-mail and any attachments is confidential. It is intended solely for the attention and use of the named addressee(s). If you are not the intended recipient, or person responsible for delivering this information to the intended recipient, please notify the sender immediately. Unless you are the intended recipient or his/her representative you are not authorized to, and must not, read, copy, distribute, use or retain this message or any part of it. E-mail transmission cannot be guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or contain viruses.