T38G "Transfer Mode via DSSkey" cannot be set to anything other than "New Call"

[Ricopreston]

Hello,
We are using Yealink T38G phones with firmware version 38.70.0.198 and a 3CX v12 SP4 server.

I am trying to test the different functions of "New call" "Blind Transfer" and "Attended Transfer."
My process;
1. I set "Transfer Mode via DSSkey" in the webpage under "Phone" --> "Features" to either "Blind Transfer" or "Attended Transfer"
2. Click "Confirm"
3. I check the setting after the page has refreshed and it is set to "New Call" again.

I have tried setting the 3CX template to force either "Blind Transfer" or "Attended Transfer" but the phone still stays on "New Call."
This happens on multiple T38G phones I have tested.
Thank you,
Eric