Voicemail and T46G freaking out

[Boolah]

PBX: Asterisk v11.3.0 with pollmailboxes=yes
T46G: Subscribe to MWI = Disabled, Subscribe MWI to Voice Mail = Disabled, Firmware Tested: 28.71.0.85, 28.71.0.105

When I get a voicemail, the T46G's power LED flashes, I get a four beeps or so through the speaker and a popup message on the LCD which says "New Voice Mail(1)". All of this is normal so far...

If I don't do anything, after some time (it could be a few seconds, 2 minutes, 10 minutes - it seems kind of random) the LCD screen will flash back to the default screen (with no popup message) followed by flashing back the "New Voice Mail(1)" popup message and flash back to the default LCD screen. It will do this three or four times per second and eventually settle back to the popup message. Sometimes it will repeat this series of flashes every five seconds or so, other times it will do this every minute or so or every 5 minutes. Again, the timing seems random. Every 10 or so of these cycles, the phone will also beep four times, just as it did to notify me that I received a new voicemail initially. The beeps are now in addition to the LCD flashes.

If I press the "View" softkey, the phone will show me the correct info for my voicemail account. Pressing the "Back" softkey brings me back to the default LCD screen. However, after a few seconds/minutes, the series of popups and flashing LCD screen returns.

If I press the "Cancel" softkey, the popup message on the LCD is cleared and I'm returned to the default LCD. Again, this will only last a few seconds/minutes before the LCD begins flashing again.

If I let the phone stay in this state (without using the phone at all or pressing any keys) for an extended period of time (over an hour). The phone will either lock up completely (I cannot press any keys on the phone at all and I cannot access the phone though its web interface) or the phone will automatically reboot itself. The only thing I can do if the phone is locked up is reboot it by pulling the PoE cable or power cycling the phone from the PoE switch.

Has anyone else experienced this before? Does anyone know if it's a config setting on Asterisk or the T46G? Is this a firmware bug? Voicemail and MWI is working correctly on all of our other non-Yealink phones. Unfortunately, I only have one T46G that I'm evaluating so can't tell if this is something specific to this phone or something more general.