Yes your best bet would be to swap out the RX for one that failsafe's on all channels. As Dave said you need to make sure that all switches/stick positions are in their failsafe position when you bind as that's how it programs them.

I always recommend genuine spektrum gear for quality and range - but it could be a couple of things if your getting back range. Simplest way is to swap out the RX and see if its OK still. Otherwise it could be a damaged aerial in the TX. It's unlikely to be the armour in your robot blacking it as in 720 its encased in 25mm thick or so aluminium all the way around and works fine (with an Orange RX too).

Its just a case of process eliminating and see where the fault lies, even if it can take abit of time!