Apply config drops grandstream phones connecting via sip-tls

hi, i have a new install of freepbx 13 (patched) and about 15 grandstream phones. the phones connect using sip-tls and srtp. the phones seem to be working good, but i have noticed that if I make a change (any change) on the pbx that requires me to hit the ‘apply config’ button, all the phones go into a “unavailable state” according to “pjsip show contacts”. at this point, the phones seem fine but the pbx has dropped them and calls go directly to voicemail. the only way I can recover is to reboot all the phones.

this seems like a bug and I would be happy to open a ticket, I just wanted to see if anyone has experienced this and maybe have a simple solution?