In the REX receiver update 1.01 released on friday 04.12.2015 was something that caused receiver to take long time bind after power-up. One user reported up to 7 seconds on Helifreak-forum.
I’ve been in email-correspondence with Jetimodel regarding my UDI-article and in there was a note:
Let me note, there is an update for the REX receivers (1.01e) on our web. There could occur RF power-up delay in firmware 1.01 published on Friday, but all other behavior is identical.
So, update your REX to 1.01e, link is here.
And now, get out and fly something :)