Paxton Net2 on draytek router drops calls instantly

[t3rm3y]

I have a site with a Paxton net2, it is registered as a sip device and calls present to it, bit when answering said calls on polycom phones the call is dropped so no speech and no ability to release the door. (Audio and door control work through the Paxton video units). The net2 did work with polycom phones when the door entry was on its own ADSL, but this has been moved over to the phone fttc line with a draytek router (dos defence is off so UDP flood defence also disabled) any ideas what is causing the calls to drop and how to fix it? The phone support team looked at the call attempts and deemed it was the Paxton not handing reinvites as the calls hit a hunt group of users.

[mavhc]

Check for any SIP "fixing" things in the router, and turn them off probably.

[t3rm3y]

Hi mavhc yes I checked on router, sip alg is off and all firewall UDP filters are off. All of the firewall helpers appear to be off in fact.

[mavhc]

Wonder why it worked before, guess you don't have sip logs from then?

[t3rm3y]

No annoyingly no logs as we were not aware the customer was changing routers and moving to the draytek. I'm asking the customer if they can force the net2 to use TCP only instead of UDP. Clutching at straws but hoping that helps.