On a fresh install of FreePBX the port configuration is
chansip 5160 / 5161
pjsip 5060 / 5061
If you leave it like that, and then log into the ATA device, leave the ATAs LOCAL sip port field set to 5060 and set it to register to xyz@IP:5160
It should then register as a chan_sip device, atleast both my HT802 and PAP2T work like this.
After changing those settings, you may have to actually power cycle the ATA devices, before they will behave with the new settings. Its either that or make sure the old connections completely expire so they will attempt to re-register, otherwise the stale connection to the old port hangs on and things dont work.
PJsip and chan_sip cannot both have 5060 AND have udp enabled, its the reason chan_sip was moved to 5160/5161 (the port is bound, atleast that was my understanding of bound ports, once you bind a port only one thing is using it.)