The stuttering can be due to different things.

- If your TX is too close to the RX, it may swamp the electronics causing all sorts of strange behavior. Lower the antenna and try from accross the room.

- WiFi and other devices can also swamp the RX electronics causing the same effect. Try to eliminate the problem with the one working servo before moving on.


That either one or the other servo works, but not both, tends to point to either:

- A problem or miswiring of the "Y" adaptor cable. Check and/or replace it.
- A low voltage condition, where the electronics supply current drops too much to power all of the servos... are the batteries properly charged? Did you undertake a "forming" charge?

The rest sounds normal. Power is provided to the electronics via one of the channels you disconnected hence the loss of functions... Though typically power is applied via the MOTOR connector.

Make sure that ALL of the connectors are oriented the same way.