Hi Vogon, I have used the same knots as you, the Albright Knot on all my rods, both for light fishing 4lb to 15lb lines, and also for heavier surf rod up to 50lb braid and leader, and it has held up with no problem, without ever unravelling. I have found it the easiest of the knots to tie Braid to leaders, and like yourself tried the Double Uni and FG but never succeeded.
The only thing I can think of is whether you are perhaps winding/looping the leader over the Braid, rather than the Braid being wound over the leader ( I hope that makes sense ) I think I made that error once and it unra