T48 Registration Failed &eadset Audio

I recently got a T48 and had 2 issues.

Issue #1:
I the phone shipped with the 35.73xx firmware.
When i originally added about 7 accounts to it they all connected and registered fine.

i went to the yealink website and upgraded to the T48-35.80.0.70.zip.
After that only 2 of my 7 accounts would register the rest would fail.
Keep in mind that i tested the accounts at the same time on another phone and they connected fine from the same network.

So i downgraded to 35.80.0.60.zip. still no luck.
i tried 35.73.0.50.zip & 35.73.193.50.zip and still nothing.

it was not until i downgraded back to the 35.73.0.40 that all my lines just started to work again.

any suggestions on this?
does anyone know what i will even be gaining from the 35.80.0.70?
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issue#2

i was previously on the T46 (Firmware 35.73.0.40) which worked great and i did not have this issue.
On the T48 with a HEADSET you can hear yourself in the headset when you talk which is very annoying.
In addition to this when not on a call and the headset light is on you can also still hear yourself in the headset.

how can i stop this?