how to detect one of bleeding amc7135 connected parallel (12x) ?
any good system?
Measure middle and left legs, should be no contact, but first , you have to remove them all. Ok ,not all ,you can leave 1, but only when if its not leaking 
middle leg is all time to negative connected, this no have sense
What do you call bleeding? AFAIK an AMC7135 driver always bleeds a bit.
That’s why I can make my own lighted redneck tailcaps by soldering a 3mm led over the switch.
The same is possible with (old) Thorfire drivers. Or the Lumintop Tool. To name a few.
The more AMC’s the brighter the 3mm led gets. With 2xAMC7135 and a UV led it is barely visible.
With 8xAMC7135 (Nanjg 105C) it is so bright I can almost use it as a keychain light.
Because AMC’s are always in parallel, with 12xAMC7135 you should be able to make a bonfire.
But I think (correct me if I’m wrong) at least some of it is caused by Schrödinger’s cat.
If you hook-up a DMM, you observe a current. Maybe that’s because the DMM is closing a circuit?
bleeding, leaks a very small current, visible on emitter.
as you said, any E-swithc lamp with amc7135 bleeding?
definitely not. only faulty amc bleeding.
“…AMC7135 driver always bleeds a bit.” - only defected or with some nasty schematics.
correct
7135 works like N mosfet only current stabilized . No input on right leg ( gate) - no output on left leg (drain). Middle (source).
seems nobody know 
because there is no easy solution, you have to unsolder all and check each separatly.