After many debugging and research I found the problem was the router on the doorphone side. I did change it but I didn’t remember so the problems all started there…
The router is a Tenda 4G03 (a 4G router). I tried disabling the firewall and everything but nothing helped. The cause I think it is the slow speed achieved by this device or some strange firmware firewall that blocks some types of connections. Switching back to the trusted YPLink Archer MR200 fixes everything (I changed it because it had some other problems).
Long story short: at least for me, do not use a Tenda 4g router with FreePBX/asterisk!