Carburettor synchronization – 1 carburettor cannot be set

Hi, everybody, I tried to synchronize the carburetors after their overhaul, but a cylinder dances out of line and I don’t get it tamed… :/ The carburetor bench was disassembled for overhaul, ultrasonic cleaned and equipped with new nozzles and seals. The float level was set to 13mm and the idle mixing screw was unscrewed 2 revolutions. The engine is running (not yet perfect) and also takes good gas, but cylinder 2 dances out of line . The clocks cross-changed – no change. As soon as I give gas, the pointer blows out. What could it be that cylinder 2 cannot be adjusted? What can I do? What do I have to do? What have I overlooked or not considered? Thank you and Best regards (the left clock has a little Macke and hangs about 0.7 afterwards)