If you've configured it on a softgate (i.e on a vSTMI), in V8, then you have the right version already. Downgrade is not a solution for whatever problem you have.
What do you mean, you configured it on HG3570 role with TDM? You are talking about the STMI on the 4K LTU? If you've added the HFA extn on a softgate, that won't be relevant.
Can you share a dis-bcsu:Tbl; and the PEN of where you added the phone ?
Maybe share your dis-sbcsu too, it could be the problem lies there.