Desk phones going red and green

[Yellow_Flash]

Hi Team,

We are running 3CX V20 update 4 on windows server.
Lately, we are having quiet a lot of issues with phones going red and green within a minute.
These phones are in the same LAN as 3cx server.
I tired the firewall checker and it passed and didnt show any issues.
This is an intermittent issue.
Sometimes the phones unregister while on call, sometimes while sitting idle.
Sometimes it is all the phones that does this, sometimes it is just one or two phones.
We are using the Cisco SPA 504 phones.
I know these are not supported phones but we haven't had a single issue with these when we were running v18.
After the V20 upgrades, the phones are acting up.

Has anyone faced such issues?
What could be the possible causes?

Thank you in advance.

 

[bitn2]

Did you configured split dns correctly? This problem could be some network problem or incompatibelity with the non supported phones. Did you tried to reprovision the phones?

 

[Yellow_Flash]

Did you configured split dns correctly? This problem could be some network problem or incompatibelity with the non supported phones. Did you tried to reprovision the phones?

Thank you for the response.
Yes. Split dns is working properly.
Yeap, couple of phones were reprovisioned, but no luck, it registers and then after sometime or the next day it unregisters and registers back. The issue is that this is an intermittent problem, but affecting all phones, sometimes together, sometimes one at a time.

 

[bitn2]

I would check one of this phones with an sbc from a different network. I think its a problem of the non supported phones or your network. Its not a 3cx problem.