I have several SPA122 ATA's running in bridge mode on a VLAN (secure from outside traffic)
All are running the latest firmware version.
All units have been fine except for one which has frozen twice. To be more specific, the web interface is responsive except for the 'voice' tab (just sits there loading in the browser forever). No dialtone is present when the problem happens.
The way I resolve it is to reboot the unit. After this it works for a few more weeks then the problem happens again.
There is an analogue bell (ringer) connected to one fxs port, and an analogue fax on the other fxs port (ATA configured for t.38).