DP750 + DP720 - Intermittently DP720's won't ring, DP750 reporting busy


DP750 and DP720 Firmware:

I have a problem where suddenly none of the handsets will ring on an incoming call (configured as parallel). The 750 is responding 486 busy. Calls during this time do show in the missed calls log though.

The only way to fix the issue is to reboot the 750.

I captured a syslog of the issue. Here are some relevant clips…

When this happens, all handsets look normal - the missed call indicator shows up on them. Rebooting the handsets has no effect.

I realize now that I only have this issue on the devices I have installed on. I have not seen this issue on my devices.

Has anyone else seen anything like this? Thanks!


Old problem is back i guess. make ticket.


I submitted a ticket.



Marcin - I’m not familiar with the “old” problem - do you happen to know what that problem was and how it can be recreated for testing?

As I said above, doesn’t have this problem - does. Support is asking me if the problem happens on - but I’m not willing to install that on a customers box without understanding exactly how to have a controlled test. (Especially since you can’t get back to once you install

I appreciate any info you might have on this. Thanks!


We noticed the same thing when running through on a DP750 connected to Freeswitch 1.10.5 using any type of registration. Calls seemed to drop after 15 minutes and the basestation would produce a core dump and reboot.

Downgraded to and the issues seem to have mostly disappeared. Grandstream replicated on firmware

Is there a pre-release I should ask them for so I might test this issue further?


DP will reject call by 486 busy (no matter of correct status of handset)


Yes, I know what the problem is - but what causes it to start doing that?

In other words, I want to recreate the problem in order to see if it is fixed on a different firmware.


Bug, no idea. It happens after some time, restart help



Could you possibly be of some assistance with this issue?

I’m not sure if there is a language issue or what - but I’m not really getting anywhere with support.

The issue appears to occur randomly - it possibly only happens when or after the DP750 is handling 2 calls. It takes a reboot to return to normal.

Support wants me to start a packet capture and then place test calls to the box until the problem happens. That simply isn’t reasonable - a single call probably won’t recreate the problem - it might take hours before it does.

Complicating matters is the fact that trying newer firmware leaves me with an unusable box because you can’t go back to - and unless the problem is fixed I can’t use the box.


I had the same thing happen to me today on version Newly configured Dp750 on Freepbx thats patched and up to date. Dp750 is configured via EPM and using pjsip. Calls to the extensions report busy and any attempt to make a call from a hand set went to busy after a delay. In EPM the extension appears to be normal and responding ( via AOR).


could possible the extension configured to use SRTP while the DP7xx didn’t enable it?
Is the codec setting correct?
A syslog will help me to troubleshoot. if you can go to the web UI syslog settings:
enable the syslog level to debug, set an fake syslog with valid IP address like, and enable SIP log in the syslog, then go to the network packets tool, capture a packets, you can download the capture with syslog included, so I can take a look at the problem.


Also, our latest firmware is https://www.grandstream.com/support/firmware
if you can set the FW server to: firmware.grandstream.com, you can upgrade the device to this one. I remember

in, we fixed: Fixed DP72x/DP730 stop receiving calls randomly.

if your issue is the same one, upgrade to will resolve the problem.


I upgraded to version so I will have to see if it happens again. Now I have an issue where line 1 keeps disappearing from HS1 and if I press the green button on then handset I don’t get dial tone but if I press speaker I do??? on HS2 when I press the green button I get dial tone in the earpiece and if I press speaker I get speakerphone.


see, green box is missing HS1 1st column.


please check your line settings, your account 1 haven’t assigned to any HS yet


you can assign your account 1 to HS 1 - Line 1, and your account 2 assign to HS 2 - Line 1, account 1 should be HS 1 mode, and account 2 should be HS 2 mode.


I did exactly that and it keep going away. I completed the upgrade to and updated the handsets too and so far it looks like its working correctly even after a few reboots. The speaker and earpeice are working correctly now too.


great! just let us know if this issue happens again, thanks!


the default URL for firmware doesnt work, if you click reset to default it goes to fw.grandstream.com/gs which does nothing. It wasnt until I changed it to firmware.grandstream.com did I get it to download and update.


nope, after an overnight, line 1 disappears again? If I try to call hs1 I immediately get a busy. The display on HS1 says “default line” instead of the extension number like before.