Trezor: spending from multisig is broken (on master)

[SomberNight]

On git master 7cf547c
python-trezor trezor/python-trezor@e618402
trezor fw 1.6.0

Created a 2-of-2 multisig wallet with trezor and xpub cosigners.

When trying to sign an ordinary txn:
(tried 1-in 1-out, and 1-in 2-out; all p2sh-multisig)

Traceback (most recent call last):
  File "/home/user/wspace/electrum/gui/qt/util.py", line 587, in run
    result = task.task()
  File "/home/user/wspace/electrum/lib/wallet.py", line 1166, in sign_transaction
    k.sign_transaction(tx, password)
  File "/home/user/wspace/electrum/plugins/trezor/plugin.py", line 58, in sign_transaction
    self.plugin.sign_transaction(self, tx, prev_tx, xpub_path)
  File "/home/user/wspace/electrum/plugins/trezor/plugin.py", line 231, in sign_transaction
    signed_tx = client.sign_tx(self.get_coin_name(), inputs, outputs, lock_time=tx.locktime)[1]
  File "/home/user/wspace/electrum/plugins/trezor/clientbase.py", line 218, in wrapped
    return func(self, *args, **kwargs)
  File "/home/user/wspace/python-trezor/trezorlib/client.py", line 151, in wrapped_f
    return f(*args, **kwargs)
  File "/home/user/wspace/python-trezor/trezorlib/client.py", line 932, in sign_tx
    res = self.call(proto.TxAck(tx=msg))
  File "/home/user/wspace/python-trezor/trezorlib/client.py", line 151, in wrapped_f
    return f(*args, **kwargs)
  File "/home/user/wspace/python-trezor/trezorlib/client.py", line 196, in call
    msg = handler(resp)
  File "/home/user/wspace/electrum/plugins/trezor/clientbase.py", line 35, in callback_Failure
    raise RuntimeError(msg.message)
RuntimeError: Error computing multisig fingerprint

Possibly broken by #3621 but not sure.

(note that it works with Electrum 3.0.5 and python-trezor 0.7.16)