The problem
After blueprinting a requester stop and placing it down, a train counter got detached from the stop. I believe it's connected entity before bleprinting (counter + stop) - you can't click on the counter and after blueprinting a counter becomes a fancy combinator you can click on.

Behaviour
After blueprinting a requester stop, the train counter becomes inoperative and you can't read trains on the way which leads to sending all the trains to the stop.

Reproduce
Place a requester stop on the track, take a blueprint and place it down.

It seems it happens only in Blueprint Sandboxes mod...