Yes we had the same problem. 3CX support is very disappointing. Wouldn't give us the time of day and left us to deal with houndreds of broken phones. Good news is, we found the bug and we are working with Polycom on an engineering fix. While we replaced the Polycom 550 phones at the company we upgraded v15 3CX, we had houndreds of VVX500 Phones that were bad after the v15 upgrate. Our support case with Polycom is on the VVX500.
Here are the issues we had after finding the problem.
Poor 3CX rollback capability. We had trouble restoring a v15 backup to v14. I am guessing the backup database cannot go backwards. Could not use v14 as too much time had passed. I sort of laughed when 3CX put automatic updates as a feature. Russian roulette?
We were not able find 3CX server download for versions specific to v15 SP0, sp1, etc so that we could roll back to a previous version within the 15 version before the SP upgrade.
I agree with Smartsoft in his comment. He hit it on the head with "Crappy company culture". I don't call them anymore.
Founded in 2005, when VoIP was an emerging technology, 3CX has gone on to establish itself as a global leader in business communications.