GATT connection timeout?

This is the first time I've come across that - I'd imagine that the actuator you're trying to connect to maybe has some kind of whitelist of devices that it allows to connect - or maybe it's to do with the bonding somehow.

The strange thing is it hangs on long enough to be able to complete the bonding...

Perhaps you could try some of the stuff I mentioned previously:

• Finding which bit of the promise actually throws the error
  
• Put a delay between the connection and getPrimaryService - it's possible that the connection event gets fired too soon, and the act of trying to get the service messes up the rest of the connection procedure