Hi all. After some mail exchange with Futaba US I've been directed to the UK agent Ripmax since I'm in europe. I posted my system with fault description to them. After three days of testing they couldn't replicate signal drop off. As a "precaution" they have replaced the whole unit and sent back to me at no cost.
It is working perfect since then so I'm happy user again.
My recommendation to all users with faulty units - replace or return.

Just to add one more thing - the range on this thing is incredible. You can drive it out of your sight